A bit is the device on a bridle that goes into the horse’s mouth to help the rider or handler guide and communicate with the horse via the attached reins.

It can be made from any number of materials, such as metal, leather, rubber or nylon, to name a few. When the bridle is adjusted properly, the bit sits well back in the horse’s mouth on a portion of the gums called the “bars,” a natural space behind the front incisors and the back molars.

Though bit styles vary by discipline, almost all fall into one of two general categories: those designed to apply direct pressure and those designed to exert leverage as well as pressure. There are also combinations of the two. Variations of these two styles can either increase the severity level for horses that fail to respond to milder bits and/or encourage the desired softening of the jaw.

It is important to select the correct bit for your riding level, as well as the horse’s sensitivity and level of training. Generally speaking, that means the mildest possible bit that is still effective on that individual horse. It’s also critical that the rider’s hands stay soft and sensitive on the reins. A well-schooled horse with a “soft” mouth needs little pressure on the bit from the rider.

The simplest bit is a direct-pressure style called the snaffle, which consists of a straight (mullen) or jointed bar mouthpiece with a plain ring on either side (to which the reins and bridle attach). There are countless variations on the basic snaffle, which is the bit with which most horses start their training. It’s also the ideal bit to continue using whenever possible, as it is not harsh.

Leverage bits amplify the pressure applied by the rider, and are therefore generally considered more severe. Because of this, their use is best left to more advanced riders with “good hands.” The most common types of leverage bits are curb bits, which have long sides called shanks and an attached curb chain or strap that sits outside the mouth in the chin groove. The reins attach to the bottom ends of the shanks. When the reins on a curb bit are pulled, they create additional pressure on the chin groove and at the poll (through the crownpiece behind the horse’s ears). This causes the horse’s jaw to yield and the neck to flex downward. The severity of a curb depends a great deal on the length of its shanks; the longer the shank, the more severe.

Another type of leverage bit is called a gag bit. In its traditional form, this bit requires a bridle with cheekpieces that slide up and down through rings or slots in the sides of the bit, generally attaching directly to the reins. Pulling on reins attached to a gag bit brings the horse’s head and neck upward. This is another type of bit that, because of its severity, should only be used by a more advanced rider.

A full or double bridle combines a small, snaffle-type bit with a curb bit in one bridle, with a curb chain in the chin groove. These, too, are for more educated hands. A pelham has many of the same properties as a full bridle in one bit. Because of this, and because its shanks are generally short, the Pelham and its cousin, the kimberwicke bit, are usually better choices for novice riders.

The severity of a bit’s mouthpiece is based on not only the material used (rubber being softer than metal, for example), but the narrowness of the mouthpiece (thin mouthpieces being harsher than wide ones). Any joint or port (raised portion) that the mouthpiece might have adds to its severity, acting on either the tongue or the roof of the mouth (or both).