For the sport, see Hammer throw. For other uses see Hammer (disambiguation).

A claw hammer on the ground.

A hammer is a tool meant to deliver blows to a target, causing it to move or deform. The most common uses are for driving nails, fitting parts, and breaking up objects. Hammers are often designed for a specific purpose, and so their design varies quite a lot. Usual features are a handle and a head, with the balance firmly in the head.The head is composed of a flat, striking surface on one end, and a peen on the other. The peen can be shaped like a claw or wedge to pull nails, or like a ball as in the ball-peen hammer.

The hammer is used in many professions, and is one of the most basic tools along with the knife.

Like the knife (and almost all tools), the hammer can also be used as a weapon. The concept of putting a handle on a weight to make it more convenient to use may well have led to the very first tools and/or weapons ever invented. In the Middle Ages, the war hammer was developed when edged weapons could no longer easily penetrate some forms of armour.

The hammer takes its place in modern weapons in the form of the firearm hammer or firing-pin hammer, a component of a firearm which strikes the percussion-sensitive part of a cartridge causing the firearm to discharge.

The use of a hammer to fix broken machinery is jokingly referred to as percussive maintenance.

Well-known forms include:

• Carpenter's hammer, including...
  • framing hammer
  • claw hammer
• Upholsterer's hammer
• Construction hammer, including sledgehammer
• Ball-peen hammer
• Cross-peen hammer
• Mallet
• Maul
• Mechanic's hammer, including ball-peen hammer
• Steam hammer
• Stonemason's or club hammer
• Firearm hammer
• Gavel used by judges and presiding authorities in general

A common adage states that "When all you've got is a hammer, everything looks like a nail."

See also

• Club
• Chisel
• jackhammer