Snap fastener

“A snap fastener (also called snap, popper, and press stud) is a pair of interlocking discs commonly used in place of buttons to fasten clothing. 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.
Snaps can be attached to fabric by hammering (using a specific punch and die set), plying, or sewing. […]
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 featured an S-shaped spring in the top disc instead of a groove.”

From Wikipedia, the free encyclopedia, http://en.wikipedia.org/wiki/Snap_fastener
Retrieved 3.1.2010