Horse Bits Design
The Horse Bits of a double bridle, showing both a type of snaffle bit called a bradoon and a curb bit. 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 Horse 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, cavesson 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 if a bit is in the curb or snaffle family, and has a great impact on the severity of the mouthpiece.
Often, horse bits with shanks and single-jointed or double-jointed mouthpieces are incorrectly referred to as snaffles. Likewise, a ported mouthpiece on a bit with direct pressure from a bit ring, such as the kimberwicke is not a curb.
The mouthpiece of a horse's bit is the first factor most people think of when assessing the severity and action of the bit. Therefore, it should be carefully considered when choosing a bit for a horse. Many mouthpieces are not allowed in certain competitions.
Bit mouthpieces may be single-jointed, double-jointed, "mullen" (a straight bar), or have an arched port in the center of varying height, with or without joints. They may also be smooth, roughened or of twisted wire or metal.
Horse Bits Combination Designs
Chifney anti-rearing bit for leading horses
Some bits combine both direct pressure and leverage, the most common examples being the Pelham bit, which has shanks and rings allowing both direct and leverage pressure on a single bit and is ridden with four reins; the Kimblewick or Kimberwicke, a hybrid bit that uses minimal leverage on a modified snaffle-type ring combined with a mouthpiece that is usually seen more often on curb bits, ridden with two reins; and the double bridle, which places a curb and a snaffle bit simultaneously in the horse's mouth so that each may act independently of the other, ridden with four reins. Another bit that combines direct pressure and leverage in a unique manner is the Gag bit, a bit derived from the snaffle that, instead of having a rein attached to the mouthpiece, runs the rein through a set of rings that attach directly to the headstall, creating extra pressure on the lips and poll when applied. Usually used for correction of specific problems, the gag bit is generally illegal in the show ring and racecourse.