Horny structure without hair or sweat glands on the fore and hind limbs of horses. They can vary greatly in size and shape but are generally oblong, between 2 and 7 cm long and between 1 and 4 cm wide. On the forelimb they are found on the inside of the forearm a hand's width above the carpus, on the hindlimb they are low down on the inside of the hock. The chestnut is thought to be a vestigial wrist pad of the first toe. Due to its highly individual shape, it can be used to identify equines.