TECHNICAL FIELD 
       [0001]    This specification relates to crown caps, and more particularly to the use of crown caps in crafting projects. 
       BACKGROUND 
       [0002]    Crown caps are commonly-used bottle caps that are often used for artistic purposes. Crown caps are used to add creative flair to bows, clothes, purses, and other craft projects. The caps are generally affixed to other materials by using glue or other adhesive, or by punching holes in the crown cap in order to sew the cap to fabric or thread ribbon through the holes. While these methods allow the cap to be attached to a project, adhesives are messy and can detach from other materials under certain humidity and temperature conditions. Punching holes in the cap alters the appearance and structural integrity of the cap. 
       SUMMARY 
       [0003]    This specification describes a crown cap having a clasp permanently attached. In general, one innovative aspect of the subject matter described in this specification can be embodied in a crown cap for crafting projects that includes a top wall comprising a substantially planar a depending peripheral flange, the flange having a plurality of ribs and a plurality of webs interconnecting the ribs; and a clasp permanently attached to the top wall wherein the clasp attached to the top wall forms an opening through which material can be passed through to secure the crown cap to an item. 
         [0004]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. The clasp is formed from a rigid material. The clasp is formed from a flexible material. The peripheral flange extends away from the top wall at least partially in a first direction along an axis that is perpendicular to a plane formed by the top wall. The clasp extends away from the top wall at least partially in the first direction along the axis. The clasp extends away from the top wall at least partially in a second direction opposite the first direction along the axis. A distance that the peripheral flange extends in a direction perpendicular to a plane defined by the top wall exceeds a distance that the clasp attached to the top wall extends along the axis. A distance that the peripheral flange extends in a direction perpendicular to a plane defined by the top wall does not exceed a distance that the clasp attached to the top wall extends along the axis. The crown cap is a metallic crown cap. The top wall is forms a substantially circular surface. The clasp is attached to the top wall in at least two places. The crown cap is a flattened bottle cap. The clasp is a ring of metal attached to the top wall in one place. 
         [0005]    In general, another innovative aspect of the subject matter described in this specification can be embodied in methods for attaching a crown cap to an item that include the actions of passing a strip of material through an opening formed by a clasp that is permanently attached to a top wall of the crown cap in at least two places, wherein the top wall has a depending peripheral flange, the flange configured to form a plurality of ribs and a plurality of webs interconnecting the ribs; and attaching the crown cap to the item by securing the material to the item. The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. Attaching the crown cap to the item by securing the material to the item comprises sewing the material to the item. Attaching the crown cap to the item by securing the material to the item comprises tying the material to the item. The item is a hair bow, a hair clip, a headband, a chain, a zipper pull, or a keychain. The clasp is permanently attached to the top wall of the crown cap in at least two places. The crown cap is a flattened bottle cap. The clasp is a ring of metal attached to the top wall in one place. 
         [0006]    The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will be apparent from the description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1A  is a perspective view of an example of a crown cap. 
           [0008]      FIG. 1B  is a top view of the crown cap of  FIG. 1A . 
           [0009]      FIG. 1C  is a bottom view of the crown cap of  FIG. 1A . 
           [0010]      FIG. 1D  is a side view of the crown cap of  FIG. 1A . 
           [0011]      FIG. 2  is a diagram that illustrates attaching the crown cap of FIG. lA to a piece of ribbon. 
           [0012]      FIG. 3A  is a perspective view of another example of a crown cap. 
           [0013]      FIG. 3B  is a side view of the crown cap of  FIG. 3B . 
           [0014]      FIG. 4  is a diagram that illustrates attaching the crown cap of  FIG. 3B  to a piece of ribbon. 
       
    
    
       [0015]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0016]    In various embodiments, a crown cap includes a clasp permanently connected to a top wall of the cap. The clasp can be attached to either the inner or outer surface of the top wall. In certain instances, the attached clasp may allow the cap to be sewn onto fabric, strung on ribbon or string, or attached to other materials. The clasp may allow the cap to be attached to various materials without adhesive and without punching holes in the cap. 
         [0017]      FIGS. 1A-1D  illustrate an example of a crown cap  100 . The crown cap  100  includes a substantially circular top wall  110  with a first side  110   a  and a second side  110   b,  a peripheral flange  120  extending from the top wall  110 , and a clasp  150 . The top wall  110 , peripheral flange  120 , and clasp  150  are each made from the same or a different material. For example, the top wall,  110 , peripheral flange  120 , and clasp  150  are made from a metal, such as aluminum, brass, stainless steel, or mild steel. 
         [0018]    The peripheral flange  120  connects to the top wall  110  along the circumference of the top wall  110 . The peripheral flange  120  extends away from the top wall  110  at least partially in a first direction along an axis A that is perpendicular to a plane formed by the top wall  110 . Thus, the peripheral flange can be part of a bottle cap or a flattened bottle cap, to name just a few examples. The peripheral flange  120  extends from the top wall  110  at an angle between forty-five and ninety degrees from the plane of the top wall  110 . The angle between the peripheral flange  120  and the top wall  110  remains substantially uniform along the length of the peripheral flange  120 . 
         [0019]    The peripheral flange  120  includes a plurality of ribs  130  and a plurality of interconnecting webs  140 . The ribs  130  and interconnecting webs  140  may extend along the entire circumference of the peripheral flange  120 . 
         [0020]    The clasp  150  is attached to the first side  110   a  of the top wall  110  in approximately the center of the first side  110   a.  In particular, the clasp  150  includes a first end  150   a  attached to the first side  110   a,  a second end  150   b  attached to the first side  110   a , and a connecting portion  150   c  that connects the first end  150   a  and the second end  150   b . The first end  150   a,  second end  150   b,  and connecting portion  150   c  are positioned on the top wall  110  such that a central axis extending perpendicular to and through a center of the top wall  110  bisects the clasp  150 . 
         [0021]    The connecting portion  150   c  is curved and forms a U-shape that extends in a second direction, which is opposite the first direction, along the axis A. The connecting portion  150   c  defines an opening or space  160  between the connecting portion  150   c  and the first side  110   a  of the top wall  110 . The space  160  is large enough for material to pass through the opening. The material can be, for example, ribbon, cloth, thread, elastic, or any other appropriate material. 
         [0022]    Although shown as being connected to the top wall  110  in two places, the clasp  150  can also be attached to the top wall  110  in one place. For example, the clasp  150  may be a ring or an ellipse of material that is connected to the top wall  110  in one place. 
         [0023]    The clasp  150  can be attached to the crown cap  100  as part of an integrated manufacturing process of the crown cap  100 . The clasp  150  can also be welded, soldered, or glued onto the crown cap  100 . The clasp  150  can be formed using any appropriate type of metal, or another appropriate flexible material, e.g., plastic, rubber, or silicone. 
         [0024]      FIG. 2  is a diagram that illustrates attaching the crown cap  100  to a piece of ribbon  170 . The ribbon  170  passes through an opening  160  formed between the clasp  150  and the top wall  110 . The ribbon can be tied to secure the crown cap  100  to the ribbon or another item, e.g., a hair bow. The crown cap  100  can also be sewed to the ribbon by passing thread through the opening  160  between the clasp  150  and the top wall  110 . The crown cap  100  can also be attached or sewed to any other type of material. For example, the crown cap  100  can be sewed onto clothing. 
         [0025]    The material to which the crown cap  100  is attached, e.g. ribbon, can also be used to attach the crown cap to other materials. For example, the crown cap  100  can be attached to the ribbon  170 , and the ribbon  170  can be attached to clothing, hair clips, hair bows, headbands, hair accessories, jewelry, beads, chains, zipper pulls, and keychains. The crown cap  100  can be attached by being tied or sewn on. The crown cap  100  can also be weaved in with beading on a string or on a chain.  FIG. 3A-3B  illustrate another example of a crown cap  300 . The crown cap  300  includes a substantially circular top wall  310  with a first side  310   a  and a second side  310   b,  a peripheral flange  320  extending from the top wall  310 , and a clasp  350 . The peripheral flange  320  includes a plurality of ribs  330  and a plurality of interconnecting webs  340 . The peripheral flange  320  connects to the top wall  310  along the circumference of the top wall  310 . The peripheral flange  320  extends away from the top wall  110  at least partially in a first direction along an axis B that is perpendicular to a plane formed by the top wall  310 . The clasp  350  can be have similar properties to the clasp  150  as described above, but the clasp  350  is attached to the crown cap  300  in in the same first direction as a direction of extension of the peripheral flange  320 . 
         [0026]    The clasp  350  is attached to the second side  310   b  of the top wall  310  in approximately in approximately the center of the second side  310   b.  The clasp  350  includes a first end  350   a  attached to the second side  310   b,  a second end  350   b  attached to the second side  310   b,  and a connection portion  350   c  that connects the first end  350   a  and the second end  350   b.  The first end  350   a,  second end  350   b,  and connection portion  350   c  are positioned on the top wall  310  such that a central axis extending perpendicular to and through a center of the top wall  310  bisects the clasp  350 . 
         [0027]    The connecting portion  350   c  is curved and extends in a first direction along the axis B. The connecting portion  350   c  defines an opening or space  360  between the connecting portion  350   c  and the second side  310   b  of the top wall  310 . The space  360  is large enough for material to pass through the opening. 
         [0028]    The clasp  350  may also have additional attachment points to the plane of the top wall  310 , thereby forming additional openings. 
         [0029]    In  FIG. 3B , the clasp  350  extends in a direction along the axis B and extends beyond the extension of the peripheral flange  320 . However, the clasp  350  can alternatively have a size such that the clasp  350  does not extend beyond the extension of of peripheral flange  320 , which can allow the crown cap  300  to be attached more securely to material. 
         [0030]      FIG. 4  is a diagram that illustrates attaching the crown cap  300  to a piece of ribbon  370 . The ribbon  370  passes through an opening  360  formed between the clasp  350  and the top wall  310 . After passing the ribbon  370  through the opening, the crown cap  300  can be secured to any appropriate material, e.g., by tying or sewing the crown cap  300  to the material. 
         [0031]    A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, more than one clasp could be attached to the cap, in a variety of different configurations. The clasps  150  and  350  are illustrated as a rigid “U”-shaped device, but the clasps  150  or  350  can have a number of other styles, shapes, and sizes. In addition, the clasps  150  and  350  are permanently attached in roughly the center of the top wall of the crown cap, but the clasps  150  or  350  can be attached to other appropriate positions of the top wall of the crown cap. Moreover, the clasps  150  and  350  extend perpendicular from the plane of the top wall, but can alternatively be attached at any appropriate angle between 0 and 90 degrees, e.g., 45 degrees, from the plane of the top wall. 
         [0032]    Accordingly, other embodiments are within the scope of the following claims.
A crown cap having a clasp permanently attached to a top wall of the crown cap. The crown cap has a top wall having a substantially planar surface, a depending peripheral flange, the flange having a plurality of ribs and a plurality of webs interconnecting the ribs, and a clasp permanently attached to the surface of the top wall wherein the clasp attached to the top wall forms an opening through which material can be passed to secure the crown cap to an item.