The market harborough is similar to the running martingale. The split straps are double the length of a regular running martingale, as they are fed up through the rings of the bit and are connected to a dee ring on the reins. The rider is able to impose more or less restriction on the upward movement of the horse’s head according to which dee ring on the rein the clips are attached to.
Contrary to the way the running martingale works, the market harborough is operated by the horse himself once in use. When the horse carries his head in the correct position, the straps through the bit rings are slack and have no effect. There is no restriction on the extension of the head and neck while jumping. It is only when the head is thrown upwards that the downward pull on the bit comes into effect.