A nipple clamp is a sex toy. It is a clamp that is applied to the nipples of a person of any gender. It causes pain by the pinching of the nipple, by the restriction of blood flow, and by the reintroduction of blood flow. Nipple clamps are used in some BDSM activities, such as breast torture. The main types of nipple clamps are the clothes-pin-style clamp, tweezer clamp, clover clamp, and piercing clamp, though any device that applies direct pressure can be used.