BACKGROUND OF THE INVENTION 
     Numerous different hand tools are used in the carpentry and similar construction trades. Skilled workers in these trades traditionally transport heavy tool boxes for storing the tools to their worksites. Along with basic tools such as hammers, screwdrivers, pliers, etc., workers and, in particular carpenters and workers who do framing, routinely require the use of layout tools, e.g. T-squares, variable angle squares, levels, measurement components for marking construction materials such as wood, metal, dry wall and plastic, circular compass drawing devices, spacing members, etc. Storage of these individual tools in a tool box naturally increases the weight of the tool box during transport. It also costs the worker valuable time in searching for a specific tool in the tool box. And given the many tools which are utilized in a particular job, it is virtually impossible to maintain all necessary tools on a work belt or otherwise on the worker&#39;s person. 
     There have been various attempts to combine hand tools used for layout functions into a single unit. However, all prior combination devices have significant deficiencies. For instance, many of these devices lack significant tool components, such as levels, compass elements, or the ability to measure and mark different material stock. Other such combination devices are heavy or otherwise cumbersome to use. Most of these prior tools cannot be readily carried on the worker&#39;s person. No current layout tool combines tool features which result in a high degree of versatility, while providing a compact, readily portable unit which is easily and efficiently configured for immediate use and a multitude of functions. 
     SUMMARY OF THE INVENTION 
     It is thus the object of the present invention to provide a multi-purpose layout hand tool which overcomes the disadvantages and limitations of existing hand tool combinations. 
     It is the object of the present invention to provide a layout tool which utilizes two primary components, configured to be used alone or connected in combination, to perform a variety of carpentry, framing, marking, layout, measurement, and like functions. 
     These and other objects of the invention are accomplished by a multi-purpose layout tool comprising an elongated main body component and a slide block component. Each component is designed to be used separately or in combination to perform a multitude of functions. An elongated opening extends substantially the length of the main body. The opening is configured to accept a slide block guide member extending from the slide block, which is secured within the opening by a threaded knob. The slide block can be adjustably secured within the opening, at designated angles in relation to the main body. The slide block also has a number of features, including dual level members and a compass pin which is used in conjunction with the main body for circular measurement, layout, and marking. 
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention, itself, however, both as to its design, construction and use, together with additional features and advantages thereof, are best understood upon review of the following detailed description with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded isometric view of the components of the layout tool of the present invention. 
         FIG. 2  is a top isometric view of the main body component of the present invention. 
         FIG. 3  is a bottom isometric view of the main body component of the present invention. 
         FIG. 4  is a top isometric view of the slide block component of the present invention. 
         FIG. 5  is a top, close-up isometric view of a section of the slide block component of the present invention. 
         FIG. 6  is a bottom isometric view of the slide block component of the present invention. 
         FIG. 7  is a bottom isometric view showing the other side of the slide block component of the present invention. 
         FIG. 8  is a bottom isometric view of the slide block component of the present invention in the compass mode. 
         FIG. 9  is a view of the present invention functioning as a T-square. 
         FIG. 10  is a view of the present invention functioning as a 45° angle square. 
         FIG. 11  is a view of the present invention functioning as a horizontal level. 
         FIG. 12  is a view of the present invention functioning as a 45° level. 
         FIG. 13  shows the present invention functioning as a compass/trammel device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Layout tool  1  comprises five basic components, main body  2 , slide block  30 , compass pin  70 , knob  80 , and washer  90 . 
     Main body  2  is an elongated unitary member, shown in the FIGs. as being twelve inches in length and two inches wide, having longitudinal axis  3 . Main body  2  comprises first elongated lateral section  4  with smooth top surface  4   a , inside surface  4   b , outside surface  4   c , and smooth bottom surface  4   d ; second elongated lateral section  6  with smooth top surface  6   a , inside surface  6   b , outside surface  6   c , and smooth bottom surface  6   d ; and end sections  8  and  10 . Elongated opening  12  extends for the majority of the length of main body  2 , parallel to longitudinal axis  3 . First lateral section  4 , second lateral section  6 , and end sections  8  and  10  completely circumscribe elongated opening  12 . First lateral section  4  and second lateral section  6  each have a given width, optimally one half inch. 
     The majority of the length of elongated opening  12  comprises open section  14 , framed by inside surfaces  4   b  and  6   b . Section  14  has a given width, optimally one inch. Section  14  opens into second section  16 , this second section has a width which is greater than the width of the first section. 
     End section  8  of main body  2  has angled surface  9  and end section  10  of the main body has outwardly extending member  11  with angled surface  13 . Hole  18  extends through end section  10  to accept a pencil  92 , when tool  1  is utilized in its compass mode, as is described hereinafter. Inset screw  19  serves to secure pencil  92  in position in hole  18 . 
     Incremental inches markings  20  on outside surface  4   c  of first lateral section  4  and markings  21  on bottom surface  4   d  are provided, representing a two way twelve inch rule. Smaller numbers  22  near markings  20  on outside surface  4   c  are provided to be utilized when tool  1  is in the compass mode. Incremental markings  23  on outside surface  6   c  of second lateral section  6  are used to determine the center of round stock from one half inch to twelve inches. 
     Slide block  30 , an independent, separate component from main body  2 , comprises base  31  having top wall  32  with smooth top surface  33 , angled front walls  34  and  36 , side walls  38  and  40  and rear wall  42 . Slide block  30 , as shown, is two inches wide by four inches long. Bottom recess  44  extends substantially the full length of slide block, beneath top wall  32 . Slide guide element  46  is secured to top surface  33 . Slide guide element  46  is a polygonal shaped block member and is shown in the FIGs. as being octagonal in shape, having flat sides  46   a ,  46   b ,  46   c ,  46   e ,  46   e ,  46   f ,  46   g  and  46   h . The diameter of slide guide element  46 , that is the dimension from one flat side to the diametrically opposite flat side, is just slightly less than the width of open section  14  of elongated opening  12 . This slight difference in width allows main body  2  to smoothly slide transversely over top surface  33  of slide block  30  without rotation of the main body, when slide guide element  46  is inserted within open section  14  of elongated opening  12 , with diametrically opposed sides of the slide guide element adjacent to inside surfaces  4   b  and  6   b  of the main body. See  FIGS. 1 ,  9 ,  10  and  13 . 
     Externally threaded member  48  comprises upper threaded section  50  extending up from slide guide element  46 . Threaded member  48  extends completely through slide guide element  46  and top wall  32  of slide block  30 , exiting into recess  44  as lower section  52 . Threaded member  48  also has open through channel  56  which extends completely through the threaded member. Internal channel threads  54  are located within channel  56 , in lower section  52 . 
     Level element  60  is located in recess  44  of slide block  30 , within side wall  40 . Level element  64 , positioned perpendicular to level element  60 , is located in recess  44 , adjacent to rear wall  42  and between side walls  38  and  40 . Level element  60  comprises level windows  61  and  62  and level element  64  comprises level widows  65  and  66 . 
     Markings “R” and “D” are provided on the surface of side wall  38  of slide block  30 . These are used for the compass function and to indicate diameter when tool  1  is used with round stock. 
     Compass pin  70  comprises elongated shaft  71  on which knurled handle  72  is secured. Pin section  73  of shaft  71  has threads  74  which extend partly along the shaft, adjacent to and on one side of handle  72 . Thread section  75  of shaft  71  has threads  76  which extend along the shaft adjacent to and on the other side of handle  72 . Shaft  71  has pointed end  77 . 
     When tool  1  is used for any function other than its compass function, pin section  73  of shaft  71  of compass pin  70  is inserted into through channel  56  of threaded member  48 . Compass pin  70  is secured and stored in this position, with its shaft  71  located within channel  56  of threaded member  48 , by the threadable engagement of threads  74  along shaft  71  and internal channel threads  54 , located within thread section  52  of the threaded member. See  FIGS. 6 ,  7 ,  9 - 12 . 
     When tool  1  is to be used for its compass function, threads  74  of compass pin  70  are threadably unscrewed from internal channel threads  54  and compass pin  70  is removed from threaded member  48 . Compass pin  70  is then rotated 180° and threads  76  of thread section  75  are screwed into internal channel threads  54  of threaded member  48 , to allow shaft  71  and its pointed end  77  to extend out from the threaded member. See  FIGS. 8 and 13 . 
     Knob  80  has outer knurled surface  82 , top surface  84 , through opening  86  with internal threads  88 , and lower base section  89 . Threads  88  are configured to threadably engage upper threaded section  50  of threaded member  48  when main body  2  is to be connected with and secured to slide block  30 . 
     Main body  2  and slide block  30 , being separate and independent components, can be used separately for different layout functions, as described hereinafter. However, these components are also designed to be connected in order to greatly increase the versatility of tool  1 . Connection of main body  2  and slide block  30  is accomplished by positioning the slide block with its top surface  33  face up, inserting slide guide element  46  into open section  16  of elongated opening  12 , aligning diametrically opposite sides, e.g. sides  46   a  and  46   e , parallel to inside surfaces  4   b  and  6   b  and sliding the main body over top surface  33  of the slide block to the desired location within open section  14  of the elongated opening. Protective washer  90  is then positioned over threaded member  48 , onto first lateral section  4  and second lateral section  6  of main body  2 . Knob  80  is next positioned over and screwed, by hand, onto threaded section  50  of threaded member  48 , until it is snug against washer  90 . 
     In this manner, main body  2  can be positioned and secured directly over slide block  30 , or as seen in  FIGS. 9-13 , it can be set and secured at a specific location over or at an angle to the slide block, by aligning different diametrically opposite sides of slide guide member adjacent to inside surfaces  4   b  and  6   b . Incremental markings  35  on top surface  33  of slide block  30  provide visual indicators of such available angles. 
     Tool  1  of the present invention is a very versatile device. The below listing of the tool&#39;s functions is provided only as selected examples, and is not to be considered inclusive of all the ways the tool can be used. 
     Main body  2  can be used separately as follows:
         as a straight edge for drawing lines   as a twelve inch ruler   as a precise tool for designating measurements of one half inch, one inch, and two inches, since the first and second lateral sections  4  and  6  are each one half inch wide and the elongated opening is one inch wide       

     Slide block  30  can be used separately as follows:
         as both a horizontal and vertical level, by positioning the slide block on its side, end, or, with knob  80  attached, inverted, with top surface  84  of the knob resting on a small surface   as a precise tool for designating measurements of two inches and four inches, the width and length of the slide block   as a straight edge       

     Main body  2  secured to slide block  30  by knob  80  can be used in combination as follows:
         as an adjustable T-square on stock  100 . See  FIG. 9     as an angle square, capable of being set at various angles. See  FIG. 10     as a horizontal and vertical level, capable of placement in different positions. See  FIG. 11     as a forty-five degree level. See  FIG. 12     for depth gauge measurement. See  FIG. 9     as a compass. By securing pencil  92  in hole  18  of main body  2  and setting pointed end  77  of compass pin  70 , a circle  94  of any measured radius up to twelve inches can be drawn.  FIG. 13  shows a five and a half inch radius circle being drawn.   as a compass trammel   for measuring round stock, including determining the radius and marking the centers of round stock       

     When all components of tool  1  are assembled, the unit becomes a compact, self-contained, integral device. Its primary components, main body  2  and slide block  30 , are fabricated of lightweight steel. It is thus configured to be stored in a case which, when provided with a strap, can easily be carried on the worker&#39;s belt or tool belt so that it is readily accessible for use. 
     Certain novel features and components of this invention are disclosed in detail in order to make the invention clear in at least one form thereof. However, it is to be clearly understood that the invention as disclosed is not necessarily limited to the exact form and details as disclosed, since it is apparent that various modifications and changes may be made without departing from the spirit of the invention.
A multi-purpose layout tool has an elongated main body component and a slide block component. Each component is designed to be used separately or in combination to perform a multitude of functions. An elongated opening extends substantially the length of the main body. The opening is configured to accept a slide block guide member extending from the slide block, which is secured within the opening by a threaded knob. The slide block can be adjustably secured within the opening, at designated angles in relation to the main body. The slide block also has a number of features, including dual level members and a compass pin which is used in conjunction with the main body for circular measurement, layout, and marking.