This application is a divisional of pending U.S. patent application Ser. No. 11/683,077, filed Mar. 7, 2007, which in turn claims the benefit of U.S. Provisional Pat. App. No. 60/780,278, filed Mar. 8, 2006, the entire contents of both prior applications being incorporated herein by reference thereto. 
    
    
     FIELD 
     The present invention relates generally to hand tools for cutting materials. In particular, the present invention relates to a handheld, manually actuated clipper for cutting structural material. 
     BACKGROUND 
     Handheld, manually actuated cutting devices are common in the art for cutting materials ranging from paper and fabrics to wood and metal. These devices, or tools, comprise such common forms as scissors for cutting paper or fabrics, clippers for cutting hedges or tree limbs and snips, punches or nibblers for cutting thin sheet metal, among an array of others. Forms of such devices are also used for piercing, nibbling, trimming, clipping, among a wide range of other applications in addition to cutting. 
     Such devices typically have two pivotally connected members that comprise handles along a first end and cutting members at or near a second end. The connection between the members is typically provided by a fulcrum generally located so as to provide mechanical advantage to the user of the device, especially in applications where materials such as wood or metal are to be cut. Designs may be tailored to provide a sufficient amount of mechanical advantage for a given application by altering the distances between the cutting members, the fulcrum and the handles. 
     The cutting members of the cutting devices in the art are also wide ranging. They may comprise one or more opposing wedge shaped surfaces or blades, for cutting or they might utilize a plurality of opposing surfaces moving in opposite directions to shear a section of material. 
     The pivotal connection between the members can be designed in various configurations as well. The configurations range from a simple pin between two members allowing pivotal movement to more complex compound action mechanical devices having multiple interconnecting members, pivot points and movements. 
     A major area for application of cutting devices or tools is the construction industry. Tools of all types, sizes and configurations are utilized to cut, pierce, nibble, clip and shear a wide variety of materials. One segment of the construction industry that employs a number of cutting tools is the fence installation business. Handheld cutting tools are used by workers in the process of assembling and installing metal and vinyl fencing. Cutting tools such as notchers, nibblers, end clippers and even saws, are commonly used in the field to prepare fencing sections for assembly by bending, forming, notching and/or cutting the fence sections to obtain a desired length or to form couplings, such as rail end steps. Handheld cutting tools are ideal for such functions due to their ease of use, portability, small size, and specificity of function. Due to the wide variety of fencing components and materials, many different tools are often necessary. 
     The materials employed in commercial, industrial and residential fencing typically comprise sections of aluminum or vinyl rails, slats, and posts among others, including preassembled panels of fencing components. The sections of structural material are often formed with unique cross-sectional profiles to provide aesthetic exterior appearances or structural strength, among other properties. Additionally, the profiles may include interior channels, or ribs, such as a “J” section, to strengthen and allow connectivity between sections, among other uses. There are many unique profiles available in the field and typically each manufacturer will produce its own unique profiles. Often, sections of the materials, whether they be preassembled panels or single components, must be cut to length in the field and the ends clipped or notched to provide a suitable coupling for joining the sections together. Couplings, such as rail end steps, generally comprise a small section or notch that is clipped from along an edge at the end of the fencing section to allow the sections to mate with a fence post. It is desirable to make the couplings with tight tolerances and without bending or deforming the remaining material in order to permit a tight connection between mating members of the fence and to produce an aesthetic appearance to the coupling. To do so, the cut should generally provide a sharp, square perimeter around the cut without unduly bending or deforming the remaining material. Producing such a cut typically requires that the material be well supported during the cut to reduce deformation and to keep the cutting blade correctly aligned with the material during the cut. Thus, each different profile of fencing material can require different tools to make the cuts and to produce quality joints. 
     The function-specific aspects of handheld tools in the art can be advantageous in providing tools specifically designed to fit a given application or material and thereby produce a good quality, clean cut or clipping. For example, the tool can be designed to produce a sharp, square cut on a specific section of material such as a fence rail having internal channels, without causing unwanted deformation to the material. 
     The function specificity of hand tools may also serve as a drawback for several reasons. The function-specific qualities of the tools limits their practical use, i.e., they can not be used, or are difficult to use, in other applications involving different materials or proprietary material shapes, among others. Thus, a single tool may be dedicated to a single task thereby requiring a worker to carry multiple tools for completing each of a variety of different tasks. Further, durable, high quality tools are oftentimes very expensive, which can be a financial burden to a worker or business when a large number of specialty tools are needed to properly complete a job. 
     There is a need for a clipper that can produce a high quality, clean cut that is easily adaptable to multiple specific functions, materials and material profiles, and has sufficient durability for extended and repeated uses. There is also a need for a clipper that can produce a high quality, clean cut for a specific material and material profile and has sufficient durability for extended and repeated uses. There is a further need for a cutting tool that can be re-configured in the field to accommodate different functions, materials and material profiles without the resorting to additional tools. 
     SUMMARY 
     A clipper having interchangeable cutting heads is disclosed according to an embodiment of the present invention. The clipper comprises an actuator separate from the cutting head which enables the common actuator to be used with multiple interchangeable cutting heads. The cutting heads are designed to be compatible with specific structural material profiles and to provide clean cuts to those profiles without causing undue deformation to the surrounding material and structure. The interchangeability of the cutting heads permits a user to utilize one actuator for multiple applications and to reduce the number of tools they must carry while on a job. For example, a user can carry a single actuator and several different heads into the field rather than multiple, dedicated tools, thereby reducing the bulk and number of tools that must be transported. Also, a user may replace or purchase new cutting heads at a lower cost as compared to purchasing a complete, dedicated tool. The cutting heads are easily interchanged through the use of a release button, a slidable punch pin lever and guide pins without the need for additional tools. Components of the cutting head are retained therein to prevent the loss of loose components in the field. 
     Alternatively, the clipper may be produced without interchangeability of the heads in order to provide a unit adapted to clipping a single structural material profile. Such a unit maintains many of the advantages of the cutting mechanism of the present invention without the addition of clipper head interchangeability. 
     An object of the present invention is a tool for cutting structural materials. The tool comprises a guide plate having a pair of spaced-apart connector pins. A pair of handles, each handle including a connector plate, are movably coupled to the guide plate. A drive pin is pivotally coupled to the connector plates, the drive pin being movable generally linearly as the handles are pivoted. A detachable cutting head comprises a body that includes a channel configured to receive a structural material workpiece. A mounting flange is coupled to the body and includes a pair of spaced-apart apertures. Lastly, a cutting plate having a connector slot is slidably disposed in the body. The apertures of the mounting flange are configured to detachably engage the connector pins of the guide plate and the connector slot of the cutting plate is configured to detachably engage the drive pin. In addition, the cutting plate is configured to move slidably in the body as the handles are pivoted, effective to cut a structural material workpiece when the workpiece is inserted into the channel of the body. 
     Another object of the present invention is a method for cutting structural materials. The method comprises the steps of forming an actuator by pivotably coupling together a pair of handles with a drive pin, and detachably engaging apertures of a cutting head to corresponding connector pins of the actuator. A slidable cutting plate of the cutting head is detachably coupled to the drive pin of the actuator. Lastly, a structural material workpiece is inserted into a channel of the cutting head and the handles are pivoted such that the cutting plate moves slidably in relation to a body of the cutting head, thereby cutting the workpiece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the inventive embodiments will become apparent to those skilled in the art to which the embodiments relate from reading the specification and claims with reference to the accompanying drawings, in which: 
         FIG. 1  is a front side elevational view depicting the general arrangement of components of an interchangeable clipper according to an embodiment of the present invention; 
         FIG. 2  is a rear side elevational view of the interchangeable clipper of  FIG. 1 ; 
         FIG. 3   a  is a front side elevational view of the head of the interchangeable clipper of  FIG. 1  depicted detached from the actuator; 
         FIG. 3   b  is a left side elevational view of the head of the interchangeable clipper of  FIG. 1  depicted detached from the actuator; 
         FIG. 3   c  is a rear side elevational view of the head of the interchangeable clipper of  FIG. 1  depicted detached from the actuator; 
         FIG. 3   d  is a top elevational view of the head of the interchangeable clipper of  FIG. 1  depicting the location of a cavity through which the blade travels; 
         FIG. 4   a  is a front side elevational view of the actuator of the interchangeable clipper of  FIG. 1  depicted detached from the head; 
         FIG. 4   b  is a rear side elevational view of the actuator of the interchangeable clipper of  FIG. 1  depicted detached from the head; 
         FIG. 5   a  is a rear side elevational view of the back plate of the interchangeable clipper of  FIG. 1 ; 
         FIG. 5   b  is a front side elevational view of the spacer plates of the interchangeable clipper of  FIG. 1 ; 
         FIG. 5   c  is a front side elevational view of the guide pin plate of the interchangeable clipper of  FIG. 1 ; 
         FIG. 5   d  is a front side elevational view of a faceplate of the interchangeable clipper of  FIG. 1 ; 
         FIG. 5   e  is a front side elevational view of a faceplate of the interchangeable clipper of  FIG. 1  depicting measurement graduations along its surface; 
         FIG. 5   f  is a front side elevational view of the blade of the interchangeable clipper of  FIG. 1  depicting a stop feature; 
         FIG. 5   g  is a front side elevational view of the cutting plate and associated punch pin lever of the interchangeable clipper of  FIG. 1 ; 
         FIG. 6   a  is a front side view of a handle and grip of the interchangeable clipper of  FIG. 1 ; 
         FIG. 6   b  is a front side elevational view of a connector plate of the interchangeable clipper of  FIG. 1 ; 
         FIG. 6   c  is a front side elevational view of the guide plate of the interchangeable clipper of  FIG. 1 ; 
         FIG. 7  is an exploded perspective view of the release button assembly of the interchangeable clipper of  FIG. 1 ; 
         FIG. 8  is an exploded view of the actuator assembly of the interchangeable clipper of  FIG. 1 ; 
         FIG. 9  is a front side, partially exploded view of the interchangeable clipper of  FIG. 1  depicting the front connector plates removed for viewing the connections between the head and the actuator; 
         FIG. 10  is a front side, partially exploded view of the interchangeable clipper of  FIG. 1  depicting the front connector plates removed for viewing the connection between the head and the actuator; 
         FIG. 11  is a front side elevation of a clipper according to another embodiment of the present invention; 
         FIG. 12  is a front side, partially exploded view of the clipper of  FIG. 11  depicting the front connector plates removed for viewing the connection between the head and the actuator; 
         FIG. 13A  depicts a cutting head according to another embodiment of the present invention with a cutter plate of the cutting head shown in a retracted position; 
         FIG. 13B  shows the cutting head of  FIG. 13A  with the cutter plate in a cutting position; and 
         FIG. 13C  shows the cutting head of  FIG. 13A  with the cutter plate in a fully-extended position. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 and 2  an interchangeable clipper tool (referred to interchangeably herein as “clipper” or “tool”)  10  comprising a cutting head  12  and an actuator  14  is disclosed according to an embodiment of the present invention. Cutting head  12  further comprises a body  16  and a cutting plate  18  which together form the cutting mechanism for clipper  10 , as depicted in  FIGS. 3   a - d . Body  16  is the housing in which the remaining components of cutting head  12  are disposed. Body  16  has at its front portion faceplates  20   a  and  20   b . Faceplates  20   a  and  20   b  are aligned generally transverse to the longitudinal axis of clipper  10  and form a portion of a channel  21  into which material to be clipped is inserted ( FIGS. 1 ,  3   a  and  3   c ). The alignment and cross-sectional profile of faceplates  20   a  and  20   b  is determinable by design such that channel  21  formed thereby can be configured to accept various material profiles (as described below). A portion of the rear side of faceplates  20   a  and  20   b , intermediate their length, is removed to form a portion of a cavity  22  extending transverse to the length of the faceplates ( FIGS. 3   d  and  9 ). Measurement graduations  23  may be included along a front portion of faceplate  20   a  and/or  20   b  to assist a user in determining the length of material to be clipped. Faceplates  20   a  and  20   b  also contain a plurality of apertures  24  through which fasteners  25  are inserted to attach the faceplates to other components of cutting head  12 . Fasteners  25  may be any type of fastener including screws, rivets, and pins, among others, or a permanent form of bonding such as welding can be used. 
     Again referring to  FIGS. 2 ,  3   b - d  and  5   a , a back plate  26  is attached at the rear side of cutting head  12  by fasteners  25  inserted through apertures  30 . Back plate  26  is generally rectangular in shape and forms the rear side of cavity  22 . A slot  28  is disposed along a central portion of back plate  26  extending transverse to the width of cutting head  12 . Slot  28  extends nearly the full height of back plate  26  and has a width suitable for accepting a punch pin lever  52  (described below). 
     Between faceplates  20   a  and  20   b  and back plate  26  is disposed a guide pin plate  32 , referred to interchangeably herein as a “guide pin plate” and a “mounting flange” ( FIG. 5   c ) and spacer plates  33  ( FIG. 5   b ), as depicted best by  FIG. 3   b . Guide pin plate  32  is typically located behind and adjacent to faceplate  20   b  and extends toward actuator  14  beyond the bottom surface of the faceplate. A bottom edge  27  of faceplate  20   b  may define the bottom portion of cavity  22 . The extended portion of guide pin plate  32  contains apertures  34  for accepting guide pins  70  of actuator  14  (described below). Guide pin plate  32  can also have sections along its width removed to provide compatibility with cutting plate  18  (as described below). Spacer plates  33  and guide pin plate  32  provide appropriate spacing between faceplates  20   a  and  20   b  and back plate  26  to form channel  21  and cavity  22 , as depicted by  FIGS. 3   a ,  3   b  and  3   d . Guide pin plates  32  and spacer plates  33  also contain apertures  36  for insertion of fasteners  25 . 
     Cutting plate  18  further comprises a widened, generally rectangular section  38  along its upper area and a neck  40  extending downwardly therefrom, as displayed in  FIG. 5   g . Section  38  contains apertures  42  for accepting fasteners  44  by which a cutting blade  46  is attached to the section. Cutting blade  46  ( FIG. 5   f ) also has apertures  48  for accepting fasteners  44 . Cutting blade  46  is a generally rectangular component having a cutting surface  49  along its upper edge. Cutting surface  49  can have any desired design that will provide adequate cutting force and ability in a given application and typically is an angled surface creating a wedge shape and a leading cutting edge  50 . Cutting surface  49  may extend across the full width of cutting blade  46  or a stop  51  can be located intermediate the width, as depicted in  FIGS. 3   a  and  5   f . Stop  51  is a portion of cutting blade  46  extending orthogonally from cutting surface  49  that forms an obstacle to the passage of material inserted into channel  21 . Stop  51  assists a user in achieving material cuts of consistent predetermined length. 
     Neck  40  provides the connection between cutting plate  18  and actuator  14  for actuating clipper  10 , as described below and depicted in  FIGS. 9 and 10 . Along the length of neck  40  is a punch pin lever  52  ( FIGS. 3   b - d  and  5   g ). Punch pin lever  52  (referred to interchangeably herein as “punch pin lever” and “lever”) interacts with slot  28  of back plate  26  to provide additional support, alignment and restriction of the movement of cutting plate  18  (as described below). Punch pin lever  52  can be any form of pin or element extending generally perpendicularly from the rear surface of neck  40  a sufficient distance to extend through back plate  26  and to provide adequate length for a user to grasp the punch pin lever and manipulate cutting plate  18 . A rubber or plastic cap  53  may be inserted over punch pin lever  52  to provide comfort to a user during manipulation of the punch pin lever and for aesthetic appearances. 
     Referring again to  FIGS. 3   a ,  3   c  and  5   g , neck  40  also contains a connector slot  54  at its end opposite section  38 . Connector slot  54  comprises a neck section  56  and a head section  58 , forming a keyhole-shaped slot. Neck section  56  typically has a short length, about ¼ inch, but may be longer or shorter depending on a given design, and has a width smaller than the diameter of head section  58 . Head section  58  is a generally circular region having a diameter greater than the width of neck section  56  and an open portion allowing communication of a release button  72  (described below) between the neck and head sections. 
     Referring now to  FIGS. 1 ,  2  as well as  4   a  and  4   b , actuator  14  further comprises handles  60 , grips  62 , connector plates  64  and a guide plate  66 . Handles  60  extend from near cutting head  12  a distance sufficient to provide a desirable amount of mechanical advantage to a user for actuating clipper  10  ( FIG. 6   a ). Grips  62  may be located on handles  60  along their extended ends to provide comfort and grip to a user during use and transport of clipper  10  ( FIG. 6   a ). Grips  62  can be composed of any suitable material including rubber, plastic, metal or wood, among others or may be integrated into the shape of handles  60 . 
     Connector plates  64  are attached along the top ends of handles  60  and interconnect handles and cutting plate  18 , as depicted in  FIGS. 1 ,  2   4   a , and  4   b . Typically, four connector plates  64  are utilized wherein each handle  60  is sandwiched between two connector plates. Attachment of connector plates  64  to handles  60  is provided by fasteners  68  which can be any form of fastener, including, but not limited to, rivets, screws, or bolts, or a bonding method such as welding, among others, can be utilized. Connector plates  64  can have any suitable shape and form desirable to provide appropriate mechanical connection between the associated components and to provide sufficient strength for operation of clipper  10  ( FIG. 6   b ). 
     As displayed in  FIG. 6   c  as well as  FIGS. 1 ,  2 ,  4   a , and  4   b , guide plate  66  is generally U-shaped and is oriented such that the ends of the U-shape point upward and away from handles  60 . Guide plate  66  provides guide pins  70  (referred to interchangeably herein as “guide pins” and “connector pins”) extending perpendicularly from its front surface near its ends. Guide pins  70  generally comprise pins fixedly attached to guide plate  66  for linking with guide pin plate  32  via apertures  34  (described below). Guide plate  66  is rotatably attached to and disposed between each set of connector plates  64  with fulcrum pins  71  inserted through the guide plate and the connector plates. The attachment is made intermediate the legs of the U-shape of guide plate  66 . 
     A release button  72  is inserted through apertures  74  through connector plates  64  thereby pivotally connecting the handles  60  together, as shown by  FIG. 8 . Release button  72  comprises a drive pin or shaft  73  having a release portion  76 , a locking portion  78 , and a flanged section  80 , as best displayed by  FIG. 7 . Release portion  76  is located at a first end of release button  72  and has a diameter smaller than the width of neck portion  56  of cutting plate  18  to allow the release portion of the release button to travel through the neck section. Locking portion  78  is adjacent to release portion  76  along the length of release button  72  and has a diameter greater than the width of neck section  56  but less than that of head section  58 . This width allows locking portion  78  of release button  72  to rotate within head section  58 , but obstructs its removal through neck section  56 . Flanged section  80  is located at the second end of release button  72  and has a diameter greater than apertures  74  through connector plates  64  to obstruct travel of the release button through the apertures. Release portion  76  and locking portion  78  have sufficient length to allow interaction with connector slot  54  of cutting plate  18 , as described below. Release portion  76  has sufficient length to allow connector slot  54  to slide around the section when release button  72  is depressed into clipper  10  and is short enough to be removed from access by the connector slot when the release button is released. Locking portion  78  has sufficient length to engage head section  58  of connector slot  54  when release button  72  is released and is short enough to fully disengage the connector slot when the release button is depressed (described in greater detail below). 
     An element  82  is attached to the first end of release button  72  to prevent its removal from apertures  74  and a biasing element  84 , such as a spring, is located between the element and the adjacent connector plate  64  to bias the release button&#39;s first end to extend away from the connector plates and to dispose locking portion  78  between the connector plates, as depicted by  FIGS. 7 and 8 . Element  82  may be any suitable shape, size and material sufficient to fixedly attach to release button  72 , and retain the release button and spring  84  in position. Spring  84  can comprise any form of spring, and is typically a helical stainless steel spring. A cap  86 , typically composed of a soft, pliable rubber or plastic is applied over element  82  to provide comfort to a user and to provide aesthetic qualities, among others. 
     As depicted in  FIGS. 1 and 4   a , a handle lock  88  may also be included between handles  60  or connector plates  64  to retain the handles in a closed position. Handle lock  88  typically comprises a rotatable, generally L-shaped member  90  located on one handle  60  and a pin  92  extending from the opposite handle. Member  90  is rotated to engage pin  92  within the L-shape to obstruct movement of the handles  60 . 
     The components of clipper  10 , described above, are typically made from a metal, such as aluminum and/or steel alloys, among other metals, unless specified otherwise, but other materials or combinations thereof may be utilized. The materials are selected to provide adequate strength to clipper  10  as well as to impart other characteristics such as, but not limited to, light weight, toughness, wear resistance, corrosion resistance, paintability, or colorability, among others. The components are also typically stamped, cut or machined, among other processes, but may be produced by any other suitable methods or combinations thereof such as casting or forging, among others. Further, any suitable form of raw materials compatible with a desired manufacturing process is useable and typically includes sheet, plate and bar stock, among others. 
     Referring now to  FIGS. 1-8  the assembly of clipper  10  is described according to an embodiment of the present invention. Cutting head  12  is assembled having cutting plate  18  and body  16 , as best depicted by  FIGS. 3   a - d . Cutting plate  18  is constructed by fixedly attaching cutting blade  46  to the front side of the cutting plate with fasteners  44  inserted through apertures  48  and  42 . Punch pin lever  52  is fixedly attached intermediate the rear side of cutting plate  18 . Cutting plate  18  is incorporated into body  16  by inserting punch pin lever  52  through slot  28  in back plate  26  and orienting the cutting plate such that cutting blades  46  extend in the direction of the top of the back plate. Fasteners  25  are inserted through apertures  30  located at each corner of back plate  26 , the fasteners extending toward the front of body  16 . Body  16  may then be constructed in layers from the rear moving toward the front utilizing fasteners  25  by first locating one spacer plate  33  along and adjacent to each side of cutting plate  18  and against back plate  26  using the fasteners along either side of the back plate and apertures  36 . Then guide pin plate  32  is located on the bottom fasteners  25  using apertures  36  such that a portion of guide pin plate extends downward and away from body  12 . Faceplate  20   a  is located on the top fasteners  25  using apertures  24  and faceplate  20   b  is located on the bottom two fasteners using the apertures. Fasteners  25  are then tightened to fixedly retain the components in place as depicted in  FIGS. 3   a - d . By this construction cutting plate  18  is slidably disposed within cavity  22  created by faceplates  20   a  and  20   b  and back plate  26 . Movement of cutting plate  18  downward and out of cavity  22  is obstructed by guide pin plate  32  and upward and downward movement is restricted by interaction of punch pin lever  52  and slot  28 . Further, channel  21  is created by portions of faceplates  20   a  and  20   b , guide pin plate  32 , spacer plates  33  and back plate  26  forming a cavity oriented across and traversing the width of cutting head  12 . 
     Actuator  14  is assembled by inserting the first ends of handles  60  into appropriately sized cavities  94  within grips  62  as shown in  FIG. 6   a . The second end of each handle  60  is disposed between two connector plates  64  and fixedly attached thereto by fasteners  68  to produce two separate handles with a pair of connector plates attached thereto, as depicted by  FIG. 8 . Such an arrangement provides space between the connector plates  64  of a width equal to the thickness of the handle  60  to which they are attached. Guide plate  66 , having a thickness generally equal to or less than that of handles  60 , is also disposed within the space between adjacent connector plates  64  and is rotatably connected thereto by fulcrum pins  71  ( FIG. 8 ). Guide plate  66  connects to each pair of connector plates  64  intermediate each leg of its U-shape, thereby linking the two separate handle  60  and connector plate assemblies. Guide plate  66  is oriented such that the legs of its U-shape point away from handles  60  and guide pins  70  extend toward the front of clipper  10 . Portions of connector plates containing apertures  74  are designed to allow overlapping of the connector plates to permit alignment of the apertures while also maintaining a gap or space between the innermost connector plates. Apertures  74  in connector plates  64  are then aligned and release button  72  is inserted from the rear side of clipper  10  through the apertures ( FIG. 8 ). Spring  84  is located around the portion of release button  72  extending from the front of clipper  10  and element  82  is fixedly attached to the end of the release button to retain the spring and release button in place. Cap  86  is then placed over element  82  ( FIGS. 7 and 8 ). 
     Cutting head  12  and actuator  14  may then be connected, as is depicted in  FIGS. 9 and 10 . Punch pin lever  52  is moved toward the top of cutting head  12  to slide cutting plate  18  upward, extending through a first cavity opening  65  ( FIGS. 3   a ,  3   d ). While retaining this positioning, guide pins  70  of actuator  14  are inserted from the rear of cutting head  12  into apertures  34  (interchangeably termed “mounting apertures”  34  herein) of guide pin plate  32 . Release button  72  is depressed toward the rear of actuator  14  to expose release portion  76  of the release button within the gap between the innermost connector plates  64 . Punch pin lever  52  is then used to slide cutting plate  18  downward through a second cavity opening  67 , causing neck  40  to insert into the gap between connector plates  64  and connector slot  54  to engage release portion  76  ( FIG. 10 ). Release portion  76  allows neck section  56  of connector slot  54  to slot in around release button  72  and allows head section  58  to engage the release button. Release button  72  is then released permitting release portion  76  to travel out of connector slot  54  and locking portion  78  to travel into and engage the connector slot. The diameter of locking portion  78  being greater than the width of neck section  56 , locks cutting plate  18  in communication with release button  72 . Cutting head  12  and actuator  14  are thereby retained in communication by guide pins  70  and release button  72 . 
     In operation, clipper  10  is typically used to clip generally rectangular portions along an edge at the end of a structural aluminum fence rail to create rail end steps according to an embodiment of the present invention. Cutting head  12  provides a channel  21  as depicted in  FIGS. 1 ,  3   a  and  3   b , into which one edge of a fence rail is inserted. Channel  21  is designed for application specific use and, therefore has dimensions closely approximating the profile of the specific fence rail to be clipped, such as the “J” section of a section of aluminum fence rail. 
     To perform a cut, handle lock  88  is first unlatched and handles  60  pulled laterally away from one another causing the handles to pivot about fulcrum pins  71 . The movement of handles  60  also draws release button  72  downward toward the users hands and therefore the attached cutting plate  18  downward, thereby removing cutting blade  46  from channel  21 . One edge of the fence rail is then inserted into channel  21 . Measurement graduations along faceplate  20   b  may be utilized by the user to determine the length of cut to be made up to the maximum length allowed by stop  51 , i.e. the fence rail can be inserted into channel  21  and against the stop to make the largest cut available or inserted any lesser amount. If a longer cut is desired, clipper  10  allows a user to make multiple adjacent cuts. 
     Once the fence rail is inserted into channel  21  a desired, measured distance, a cut is made by manually actuating clipper  10  by pressing handles  60  together. Such movement of handles  60  actuates release button  72 , cutting plate  18  and cutting blade  46  upward through cavity  22  and into channel  21 . Cutting edge  50  is thereby pressed into and cuts through the material. Cutting surface  49  provides additional cutting action and causes the cut material to be ejected from cutting head  12  through the top open end of cavity  22  ( FIG. 3   d ) when the cut is complete. Body  16  and channel  21  retain and support the fence rail during the cut, thereby reducing the amount of deformation caused to the fence rail and any features thereon. Upon completion of the cut, the fence rail may be removed from channel  21  or inserted further for subsequent cuts. Only one side or edge of the fence rail is cut at a time, thus allowing a user to have cuts of differing lengths on either side of the fence rail to increase adaptability of the fence rail to angled or slanted applications on uneven ground, among other advantages. 
     Clipper  10  provides a material profile specific channel  21  in cutting head  12  to increase cut quality of unique and specific material profiles. Clipper  10  accommodates multiple different material profiles by permitting interchangeability of cutting head  12 . Multiple cutting heads  12  are available, each for a different specific material profile, and are easily and similarly attached and detached from actuator  14 . Cutting heads  12  may also be designed to accommodate various materials and for use in other applications such as, but not limited to, vinyl fencing installation, aluminum siding, and plumbing installation. 
     To detach cutting head  12  the reverse process of that described above is followed. Release button  72  is depressed to reintroduce release portion  76  into connector slot  54  and punch pin lever  52  is slid upward to disengage the connector slot from the release button (see  FIGS. 9 and 10 ). Cutting head  12  is then moved toward the front of clipper  10  to disengage guide pins  70  and the cutting head removed. A different cutting head  12  may then be attached for cutting a different material profile, different material, or to replace old, worn out or lost cutting heads. 
     Referring now to  FIGS. 11 and 12 , a clipper  100  is depicted according to another embodiment of the present invention. The structural profile-specific cutting functions and characteristics of clipper  10  are included in a non-interchangeable unit, clipper  100 . Clipper  100  is generally constructed as described above but without the ability of interchangeable cutting head  12  to accommodate multiple structural profiles. For example, the release button  72  may be replaced with an actuator pin  196  much like that of fulcrum pins  71  and guide plate  66  replaced with guide plate  166  which is similar in structure to guide plate  66  but with extended legs that are affixed to cutting head  112 . Guide pin plate  32  and spacer plates  33  may be omitted from cutting head  112  and their functions replaced by the extended portions of guide plate  166 . Alternatively, another embodiment of cutting head  112 , having a single piece body  116  or other variations of the above components, may also be utilized so long as the functional aspects of the cutting action of cutting blade  146  within cavity  122  and channel  121  are retained. Additionally, the utilization of a structural profile-specific channel  121  is maintained in order to provide a good quality, clean cut without causing unwanted deformation to the surrounding material. 
     A head  212  is shown in  FIGS. 13A ,  13 B and  13 C according to another embodiment of the present invention. Head  212  is similar in structure and function to heads  12 ,  112 , wherein a cutter plate  218  is captively and slidably disposed within a body  216 . Cutter plate  218  includes a punch  246  configured to selectably slidably extend into a cavity  222 , moving generally perpendicularly to a channel  221 . With general reference to  FIGS. 1 and 13A , in operation head  212  is detachably mounted to an actuator  14  in the manner previously described for heads  12 ,  112 . A material to be punched is inserted into channel  221  with handles  60  in an open, spread-apart position with respect to each other. With general reference to  FIGS. 1 and 13B , handles  60  are then pivoted toward each other, urging punch  246  through the material and into cavity  222 , thereby punching an aperture in the material corresponding to the shape of punch  246 . In various embodiments punch  246  may be shaped to form apertures having various shapes and sizes. Examples include, without limitation, square, rectangular, circular and polygonal apertures. Cutter plate  218  may be moved to a fully-extended position as shown in  FIG. 13C  to facilitate removal of head  212  from actuator  14 , which is accomplished in the same manner as described above for heads  12 ,  112 . The structure and function of the remaining components of head  212  are substantially the same as heads  12 ,  112  and thus will not be reiterated here. 
     As can be seen from the foregoing, the embodiments of the present invention solve a number of the shortcomings of tools in the art. For example, with reference to  FIGS. 1 and 11 , heads  12 ,  112 ,  212  are easily coupled to actuators  14 ,  114  respectively without the need to resort to tools. Likewise, heads  12 ,  112 ,  212  may be detached from actuators  14 ,  114  respectively without the use of tools. Thus, tools  10 ,  100  may be conveniently configured for cutting a variety of structural materials by changing heads  12 ,  112 ,  212  respectively to a head configured to cut a particular shape or type of structural material. This is particularly beneficial when tools  10 ,  100  are in use at a remote location where adjustment tools are inconvenient to use or are unavailable. 
     While this invention has been shown and described with respect to a detailed embodiment thereof, it will be understood by those skilled in the art that changes in form and detail thereof may be made without departing from the scope of the claims of the invention. For example, one skilled in the art will recognize that the components of heads  12 ,  112 ,  212  may be shaped and arranged to cut or punch one or more predetermined shapes in or through structural materials having various shapes and profiles.
A method for assembling a tool for cutting structural materials includes the steps of providing a pair of handles, each handle having a connector plate. A drive pin is pivotally coupled to the connector plates, the drive pin being movable as the handles are pivoted. A detachable cutting head includes a body with a cavity having a pair of opposing cavity openings, and further includes a channel to receive structural material workpieces. A cutting plate is slidably disposed in the cavity. The cutting head is selectably coupled to the handles and the cutting plate moves slidably in the body as the handles are pivoted, cutting a structural material workpiece inserted into the channel of the body, a cut portion of the inserted structural material workpiece being ejectable through the first cavity opening.