Gag Bits Explained
The sliding action of a Gag Bit applies pressure to the horse’s lips and corners of the mouth. The bit is allowed to slide up the cheeks of the bit to tighten the distance between bit and poll. In the case of a simple rope gag bit, they also apply pressure to the poll as the bit slides up the shank or rope. Severity is determined by the ring size: the larger the rings, the more severe the gag.
The gag bit normally is used with two sets of reins; one on the bit ring that does not apply gag leverage, and the other on the small ring attached to the cord or rolled leather strap of the gag bridle cheekpiece. This allows for the bit to be used as a normal snaffle (most of the time), with gag action used only when your horse gets strong.
It is helpful to use two reins of different material (ie: one flat and one braided) to help the rider differentiate between the reins by feel.
Gag bits are often used to encourage elevation in the front end and to rebalance a horse before a jump. They are frequently used by lighter or smaller riders riders with strong horses who need more braking leverage. A gag is too severe for a heavy-handed rider or a rider who does not have very good balance and a very good seat.
They are not permitted at any level of dresssage, since dressage riders are trying to get the horse to come down onto the bit, and want to encourage the horse to accept contact. They are also never seen in the hunter arena. They are sometimes used for polo and show jumping.
They are not used as an everyday bit. Frequently used for warm-up or fine-tuning.