Normally used as a demolition tool, they may be mounted on a hammer drill, jack hammer, or hammered manually, usually with a heavy hammer of three pounds or more.
Hammer drills are more expensive and more bulky than regular drills, but are preferable for applications where the material to be drilled -- concrete block or wood studs -- is unknown.
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.
