Nail

A Nail is a slender, typically rod-shaped rigid piece of metal, usually in any of numerous standard lengths from a fraction of an inch to several inches and having one end pointed and the other enlarged and flattened, for hammering into or through wood, other building materials, etc., as used in building, in fastening, or in holding separate pieces together.

It can also mean a thin, horny plate, consisting of modified epidermis, growing on the upper side of the end of a finger or toe.