At the heels, the palmar/plantar portions of the walls bend inward sharply, following the external surface of the collateral grooves to form the bars. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating keratinised material, called the 'sole'.
The edges of the hoof have an inward bend, tracing the external contours of the collateral grooves to create the bars. The underside of the hoof, including the outer walls and the inner frog and bars, is protected by a layer of shedding keratin material known as the 'sole'.