thumb|225px|A model wearing two nipple clamps joined by a chain. The chain is held in the model's mouth to pull the nipples upwards.
A nipple clamp is a type of sex toy that is applied to a person's nipples to pinch them. Varieties of nipple clamp include clothes-pin-style, tweezer and clover. Nipple clamps are used to cause pain in the nipples as part of certain BDSM activities. They are also used to produce erotic stimulation as part of nipple play. In this context they are not primarily used to produce pain but rather to increase nipple sensation. Their use traps blood in the nipples, increasing the sensitivity of the nipple. The sexologist Carol Queen says that "clamps are also very useful for hands-free nipple play".
Technique
As the nipples are an erogenous zone, nipple clamps can be used to heighten sensation and may lead to orgasm. BDSM practices, such as the use of a safeword, are often employed when nipple clamps are used. Before the clamps are applied, the nipples are typically stimulated manually or orally to prepare them. Once the nipples are erect and the "jaws" of the clamps are closed slowly, If the blood circulation to the nipple is cut for too long there is also a risk of damage to the tissue and nerves. Changes in skin colour can be used to determine the level of blood flow, which needs to be re-established regularly to prevent any permanent damage. When the clamps are removed, the restricted blood flow rushes back into the nipples and releases oxytocin, a hormone associated with orgasm. This can make skin sensations more intense and pleasurable. Another use for the clamps is to keep a person in one place. If a cord is tied from the clamp to a fixed place, the wearer of the clamps cannot move away because the clamps will tighten as they move. This technique can be used for predicament bondage. The removal of the clamps is also painful and different methods of removal can increase or decrease this pain.
Magnetic clamp
A magnetic clamp pinches the nipple between two strong magnets. The pressure applied cannot be varied in the way that it can using adjustable clamps. Magnetic clamps typically produce a high level of pain akin to clover clamps and are more suitable for experienced wearers.