A knockout punch is a handheld tool used to punch a hole through sheet metals, plastics and other solid materials. A knockout punch consists of a punch, die and screw and can be driven by hand, a ratchet, or with hydraulics.
Knockouts all function similarly. A pilot hole is drilled into the sheet or wall to guide the punch. The die and punch are placed on the opposite sides of the sheet and the screw threaded through. As the screw tightens, the punch cuts the hole. A knockout can also be han- or ratchet-operated to simplify the process. The punch and die are simply squeezed together with one tool, without any mechanical assembly.
Knockouts are used extensively in metalworking applications and for outfitting enclosures. Holes are punched to feed cables into a sealed box or cabinet.