The two halves of a riveted leather "snap"; the male half (top) has a groove which "snaps" in place when pressed into the female half (bottom)
A snap fastener (also called snap, popper, and press stud) is a pair of interlocking discs, made out of a metal or plastic, commonly used in place of buttons to fasten clothing and for similar purposes. A circular lip under one disc fits into a groove on the top of the other, holding them fast until a certain amount of force is applied. Snap fasteners are often used in children's clothing, as they are relatively easy for children to use.
Different types of snaps can be attached to fabric or leather by riveting with a punch and die set specific to the type of rivet snaps used (striking the punch with a hammer to splay the tail), sewing, or plying with special snap pliers.
Modern snap fasteners were first patented by German inventor Heribert Bauer in 1885 as the "Federknopf-Verschluss", a novelty fastener for men's trousers. Some attribute the invention to Bertel Sanders, of Denmark. These first versions had an S-shaped spring in the "male" disc instead of a groove. When Jack Weil (1901–2008) modified the design and put snaps on his iconic Western shirts, the term "snap" became commonplace and snap fasteners came into use in much Western wear.