A horse carries a bit in its mouth, held on by a bridle.
A bit used in equestrian activities is a piece of metal or similar synthetic material that is placed in the mouth of a horse or other equid and allows a rider to control the animal. It rests on the bars of the mouth in an interdental region where there are no teeth. It is held on a horse's head by means of a bridle and has reins attached for use by the rider.
Although there are hundreds of design variations, the basic families of bits are defined by the way in which they put pressure on the mouth, and include:
Snaffle bit: A direct pressure bit
Curb bit: A bit that uses a type of lever called a shank to achieve additional pressure though use of leverage
Pelham bit: A single bit with a shank that combines snaffle and curb pressure
Kimberwicke: A hybrid design that uses a slight amount leverage on a bit ring by use of set rein placement on the ring
Gag bit: A bit that achieves leverage by sliding up in the horse's mouth, a very severe design.
A type of bridle that carries two bits is called a double bridle or Weymouth.
Bits are further described by the style of mouthpiece that goes inside the horse's mouth as well as by the type of bit ring or bit shank that is outside the mouth, to which the reins are attached.
Bridles that do not use bits are usually called hackamores.
The first bits were made of rope, bone, horn, or hard wood. Metal bits came into use between 1300 and 1200 BC, originally made of bronze. Stainless steel is the most popular material used today, although copper and "sweet" iron (cold rolled steel) are incorporated into some bits to encourage salivation in the mouth of the horse and hence a softer mouth. Other materials such as rubber or plastic are also used, sometimes in combination with metals.
Throughout history, the need for control of horses in warfare drove extensive innovation in bit design, producing a variety of prototypes and styles over the centuries, from Ancient Greece into modern day use.
Design and terminology:
A bit consists of two basic components, the bit mouthpiece that goes inside the horse's mouth, and the bit rings of a snaffle 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, cavesson on the jaw and face, or pressure on the poll from the headstall. Particular mouthpieces do not make a bit a snaffle or a curb. 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, bits with single- 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.
The mouthpiece of the bit does not rest on the teeth of the horse, but rather rests on the gums or "bars" of the horse's mouth in an interdental space behind the front incisors and in front of the back molars. When a horse is said to "grab the bit in its teeth" they actually mean that the horse tenses its lips and mouth against the bit to ignore the rider's commands (although some horses may actually learn to get the bit between their molars).
Bits are designed to work by pressure, not pain. Depending on the style of bit, pressure can be brought to bear on the bars, tongue, and roof of the mouth, as well as the lips, chin groove and poll. Bits offer varying degrees of control and communication between rider and horse depending upon their design and on the skill of the rider. It is important that the style of bit is appropriate to the horse's needs and is fitted properly for it to function properly and be as comfortable as possible for the horse.
In the wrong hands even the mildest bit can hurt the horse. Coversely, a very severe bit, in the right hands, can transmit extremely subtle, nuanced signals that cause no pain to the horse. Commands should be given with only the quietest movements of the hands, and most steering is done with the legs and seat. Thus, instead of pulling or jerking the horse's head to change direction by force, a skiller rider indicates the desired direction by tightening and loosening the grip on the reins. The calf of the leg is used to push the body of the horse in a certain direction while the other one is used as a pivot and to provide the correct amount of impulsion required to keep the horse moving. Likewise, when slowing or stopping, a rider sits deeper in the saddle and closes their hands on the reins, avoiding jerking on the horse or hauling back on the reins in a "heavy-handed" fashion. Change of position of the seat and the pressure of the rider's seatbones are also extremely useful for turning, speeding up and slowing down.
There are many factors in the bitting equation which must be consided to get a true estimate of the action and severity of a bit. Although some mouthpieces are marketed as "correction" (a euphemism for "severe") bits or "training" (implying a mild bit), the terms are relative. The bit always rests on the sensitive bars of a horse's mouth. A hard-handed rider can make even the mildest bit painful, and a skilled, light-handed rider can ride in a much harsher mouthpiece without damaging the mouth or causing any distress in the horse. Additionally, the shank or ring has a great impact on the action of the mouthpiece. Snaffles are generally considered the mildest, curbs and gags the harshest. It is difficult, therefore, to compare a harsher-type bit with a mild mouthpiece (such as a pelham with a rubber mullen mouth), and a milder-type bit with a harsher mouthpiece (like a thin snaffle with a slow twist). In general, however, the mouthpiece can have a marked difference on the severity. Snaffles with twisted wires are never considered mild, while a pelham with a low port may.
Snaffle or direct pressure bits:
All bits work with either direct pressure or leverage. Bits that act with direct pressure on the tongue and lips are in the general category of snaffle bits. Snaffle bits most commonly have a single jointed mouthpiece and act with a nutcracker effect on the bars, tongue and occasionally roof of the mouth. However, any bit that operates only on direct pressure is a "snaffle" bit, regardless of mouthpiece.
Curb or leverage bits:
Bits that have shanks coming off the bit mouthpiece to create leverage that applies pressure to the poll, chin groove and mouth of the horse are in the category of curb bits. Most curb bit mouthpieces are solid without joints, ranging from a straight bar with a slight arch, called a "mullen" mouthpiece, through a "ported" bit that is slightly arched in the middle to provide tongue relief, to the full spade bit of the Vaquero style of western riding which combines both a straight bar and a very high "spoon" or "spade" extension that contacts the roof of the mouth. The length of the shank determines the degree of leverage put on the horse's head and mouth. Again, a bit with shanks and leverage is always a "curb" type bit, even when it has a jointed mouthpiece more commonly seen on a snaffle (such bits are sometimes incorrectly called "cowboy snaffles"). All shanked bits require the use of a curb chain or curb strap for proper action and safe use.
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.
In popular culture:
Bits and the behavior of horses while wearing bits have made their way into popular culture outside of the horse world.
Took the bit in his teeth, a phrase that describes a horse that sets its jaw against the bit and cannot be controlled (rarely does the horse actually grab the bit with its molars), is used today to refer to a person who cannot be controlled or who is charging ahead without consideration of the consequences.
Champing at the bit, or chomping at the bit refers to a tendency of some horses, when impatient or nervous, and especially if being held back by their riders, to chew on the bit, often salivating excessively. This behavior is sometimes accompanied by head-tossing or pawing at the ground. Because this behavior was most often seen by the general public in horses who were anxious to begin a horse race in the days before the invention of the starting gate, the term has become popular in everyday speech to refer to a person who is anxious to get started or to do something. Because some impatient horses, when held back, would also occasionally rear, a related phrase, "raring to go," is also derived from observations of equine behavior.