A chambon is a piece of horse tack. It is a strap that runs forward from the bottom of the girth or surcingle, and forks. The forks continue to a ring on either side of the bridle or halter, at the base of the crownpiece. Running through those rings, the forks follow the cheekpieces to the bit. They may attach to the bit or pass through the bit rings and attach to themselves below the horse's neck.
A chambon prevents the horse from raising its head beyond a fixed point. Raising the head causes the length of the chambon along the cheekpieces to shorten and thus puts reciprocal pressure on the horse's mouth and behind the horse's poll. Horses generally dislike pressure behind the poll and learn to release the pressure by lowering their head. Although the chambon is used mostly in training horses via longeing, it is used also in riding.
Use in longeing
The chambon was originally intended for longeing and free schooling.
Chambons are advanced equipment, and should only be used by knowledgeable trainers who are excellent in the art of longeing. A chambon is not a way to quickly fix the head set of a horse. It is merely to help develop the correct muscle. Chambons help a horse to develop the muscles of their back and topline. It applies pressure to the poll and mouth of the horse when he raises his head, releasing when the horse stretches long and low, down toward the ground. When a horse is lunged correctly, and the chambon is correctly adjusted, the horse stretches down and raises his back.
Before using a chambon, it is important to teach a horse to give correctly while worked in hand. If not, the horse may not know to lower his head to the pressure, may panic when he feels the upward and ungiving pressure on the bit, and possibly rear. The advantage of the chambon is that it only comes into effect when the horse raises his head, so the horse has some control on its action. It generally works very well on horses in adjusting their head position. However, it has no direct effect on the hindquarters, so it must be used skillfully.
If a horse is not lunged properly, he may begin to go on his forehand. Chambons can also cause sore neck muscles. Incorrect use can therefore spoil a horse's gaits, which would then require weeks of retraining.