A cotter pin is a metal fastener with two tines that are bent during installation. This function is similar to a staple or rivet. It is typically made of wire with a half-circular cross section, a new cotter pin that has its flat inner surfaces touching one another for most of its length, so that it appears to be a split cylinder. Once inserted, the two ends of the pin are bent apart, locking it in place. In order to facilitate the initial separation of the tines, one tine of the cotter pin is often noticeably longer than the other. Cotter pins are frequently used to secure other fasteners.