A caveson is part of a horse bridle or in a heavier version is used for longing. This is called a lounge caveson. In either case cavesons are a band of leather that goes around a horses lower face above the nostrils and have another strap that goes around the head behind the ears.When used with a bridle it's purpose is to keep the mouth closed so that the horse cannot evade the bit. A lunge caveson is used in ground work for the purpose of control while training. The lunge caveson is a much heavier piece of equipment and has rings attached over the nose for attaching a lounge line.Thus affording control of the horses head.