 A bit consists of two basic components, the bit mouthpiece that goes inside the horse's mouth, and the "bit rings" of a snaffle bit or "shanks" of a curb bit, to which the bridle and reins attach.All bits act with some combination of pressure and leverage, often in conjunction with pressure applied by other parts of the bridle such as the curb chain on the chin, noseband on the jaw and face, or pressure on the poll from the headstall.Particular mouthpieces do not define the type of bit.