Clamps are a sex toy made to be applied to the nipples, genitals or other body parts of a woman or a man. The erotic pleasure is derived by a masochist from enjoying such pain and by a sadist from inflicting such pain. They are used in many BDSM activities, such as breast, pussy or tongue torture.
The main types of clamp are the clover clamp, tweezer clamp, piecing clamp, and clothes-pin style, though any device that applies direct pressure can be used. Weights may be hung from the clamps to amplify the pain by increasing the pressure and pinching. Clamps can be fixed to a piece of erotic furniture such as a post, so that when the wearer is prodded to jump or otherwise move suddenly by, say, erotic spanking or caning, the pain is amplified by the clamps being pulled, greatly increasing the pinching. A selection of excellent clamps of all types can be found and bought here.