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. It is the sidepieces and the leverage these rings or shanks use to act on a horse's mouth that determines whether a bit is in the curb or snaffle family, and has a great impact on the severity of the mouthpiece.