A hammer drill is a power tool used to bore holes through tough surfaces such as concrete, brick, or stone. It is a type of rotary drill with an impact mechanism that generates a cam-action or percussion hammering mechanism. Hammer drills look and act like traditional power drills, with standard chucks, triggers, and speed controls, but they are larger and more powerful. The hammer function of a hammer drill is activated by the user and causes the drill to punch the tip of the bit forward into the material, making short work of an otherwise monotonous task. Hammer drills are not typically used for production construction drilling, but rather for occasional drilling of holes into concrete, masonry, or stone. Some common uses for hammer drills include:

• Starting and drilling a hole on a slippery tile or glass backsplash.
• Drilling through basement concrete to attach framing lumber.
• Drilling into concrete steps for attaching handrails.
• Hanging TV wall mounts, shelves, or pictures on brick.

Hammer drills are more expensive and more bulky than regular drills, but they are indispensable for drilling into hard materials. Hammer drills almost always have a lever or switch that locks off the special "hammer clutch," turning the tool into a conventional drill for wood or metal work.