A round fastener is a type of closure that is used to secure two objects together. The most common type of round fastener is a SNAP, which is a four-letter word. A SNAP consists of two interlocking discs, often made of metal or plastic, which are held together by a spring-like action. When the discs are pressed together, they form a secure closure. Snaps are commonly used in clothing, bags, and other items where a secure closure is needed.