The iron bit, also referred to as a gag, was used by enslavers and overseers as a form of punishment on slaves in the Southern United States. The bit, sometimes depicted as the scold's bridle, uses similar mechanics to that of the common horse bit. The scolds bridle however, is almost always associated with its use on women in the early 17th century and there are very few accounts of the device as a method of torture against black slaves under that particular name. As opposed to the whip, the iron bit lacks the historic, social, and literary symbolic fame that would make information on the use of the iron bit as accessible. Its use throughout history has warranted some attention though, mostly from literary texts. Even earlier, slave narratives and publications of newspapers and magazines from the 18th century on give evidence of this device being used to torture and punish slaves.

A scold's bridle, sometimes called a witch's bridle, a gossip's bridle, a brank's bridle, or simply branks, was an instrument of punishment, as a form of public humiliation. It was an iron muzzle in an iron framework that enclosed the head. A bridle-bit, about 5 cm × 2.5 cm in size, was slid into the mouth and pressed down on top of the tongue, often with a spike on the tongue, as a compress. It functioned to silence the wearer from speaking entirely, to prevent the women from nagging. The scold's bridle was used on women. This prevented speaking and resulted in many unpleasant side effects for the wearer, including excessive salivation and fatigue in the mouth. For extra humiliation, a bell could also be attached to draw in crowds. The wearer was then led around town by a leash.