Coloured scanning electron micrograph (SEM) of Tip of a finish nail. A nail is a pin-shaped, sharp object of hard metal (typically steel) used as a fastener. Nails for specialized purposes may also be made of stainless steel, brass or aluminium. Nails are typically driven into a material (typically wood) by a hammer or by a nail gun. A nail holds materials together by friction in the vertical direction and shear strength in lateral directions. One point of the nail is also sometimes bent over or clinched to prevent it from pulling out. Magnification: x8 when shortest axis printed at 25 millimetres.