Nail (fastener)

A pile of nails
Classification	fastener
Used with	wood, concrete

In woodworking and construction, a nail is a pin-shaped object of metal (or wood, called a treenail or "trunnel") which is used as a fastener, as a peg to hang something, or sometimes as a decoration. Generally nails have a sharp point on one end and a flattened head on the other, but headless nails are available. Nails are made in a great variety of forms for specialized purposes. The most common is a wire nail. Other types of nails include pins, tacks, , and cleats.

Nails are typically driven into the workpiece by a hammer, a pneumatic nail gun, or a small explosive charge or primer. A nail holds materials together by friction in the axial direction and shear strength laterally. The point of the nail is also sometimes bent over or clinched after driving to prevent pulling out.

The history of the nail is divided roughly into three distinct periods:

To make a wrought-iron nail, iron ore is heated with carbon (to create wrought iron) and shaped into square rods. To make a nail, a blacksmith heats the rod in a forge and tapers the end of the bar while keeping the cross section square. Next, the smith cuts off the taper, and inserts it into a nail heading tool with a square hole. The top of the taper is hammered downward (upset) to form a head.

Nails date back at least to Ancient Egypt — bronze nails found in Egypt have been dated 3400 BC. The Bible provides a number of references to nails, including the story in Judges of Jael the wife of Heber, who drives a nail (or tent-peg) into the temple of a sleeping Canaanite commander; the provision of iron for nails by King David for what would become Solomon's Temple; and in connection with the crucifixion of Christ.

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