A ring made of rubber, steel or leather that fits tightly over the base of a penis or over the penis and testicles to help maintain an erection, or to make the genitals appear larger. Cock rings hold shut the veins near the surface of the penis so the penile blood pressure does not escape. They are of somewhat dubious value, and should not be worn for more than 20 or 30 minutes without being taken off for a few minutes. Otherwise, there is a risk of permanent damage. In BDSM, a cock ring can be used on a submissive to denote ownership. It can also be worn as jewelry when hung from a chain around the neck. If a cock ring that is made of steel gets stuck on a swollen penis, it will require a trip to a hospital to have it removed, where they may have to call in a locksmith or welder. This is why it is best if the ring is made of rubber or leather, or if it is metal it should have a hinge for easy opening.