in tetrapods, claws are made of keratin and have two layers. the unguis is the outside hard layer, which has keratin fibers arranged perpendicular to the direction of growth and in layers at an angle. the subunguis is the soft, flaky layer, and the grain is parallel to the direction of growth. the claw grows outward from the nail matrix at the base of the unguis and the subunguis grows thicker while traveling across the nail bed. the unguis grows outward faster than the subunguis to make a curve and the thinner sides of the claw wear away faster than their thicker middle, making a more or less sharp point. tetrapods use their claws in many ways, such as grasping or killing prey, digging, climbing, and hanging.