Paulin Snap Fasteners provide superior snap action and holding strength. Snap Fasteners are self-piercing and made of heavy duty, nickel plated brass. Used in a variety of materials on boats, tents, sporting goods, RV's, luggage, awnings, clothing - camper, convertible and tonneau covers. Snaps consist of 4 parts to make a set. Caps, Sockets, Studs and Posts. The socket part fits in the cap (top part of snap). The cap is the smooth side that is fitted to the material. The post that fits in the Stud (bottom part of snap). When the post expands, it creates a tight fit. Some materials may require pre-drilling before inserting the snaps.