The underside of a horse’s hoof is called a frog

horse hoof

The frog is a part of a horse’s hoof, located on the underside, which should touch the ground if the horse is standing on soft footing. The frog is triangular in shape, and extends from the heels to mid-way toward the toe, covering around 25% of the bottom of the hoof. The frog acts as a shock absorber for the foot when it makes impact with the ground, decreasing the force placed on the bones and joints of the leg.