A Hitchcock gag uses a slightly different mechanism than the more typical eggbutt gag. In this case the bit itself looks basically like a Boucher snaffle. However, pulley rings that attach to the bit and to the headstall make it possible to put extreme amounts of pressure on the horse’s head. The rein attaches to the upper ring of the bit, passes up the cheek and through the pulley ring on the side of the head stall, passes back down the cheek and through the pulley ring on the snaffle ring of the bit and onward to the rider’s hand.
This double pulley system gives the rider extreme mechanical advantage, allowing intense pressure to be put on the mouth and poll. Needless to say, this is a system to be used only in extreme situations, if ever, and only in the hands of experts.