A circlip is a flexible mounting- or retaining ring, usually made of metal, with open ends. The retaining ring can be snapped into place in the machined groove to allow rotation but to prevent lateral movement. There are two basic types, external (DIN471) and internal (DIN472), which indicates whether they are mounted in a hole or over a shaft. Circlips are often used to protect pin joints. The retaining ring is also commonly known as a Seger ring, a locking ring and a retaining ring.