A hacksaw is a hand-powered saw with a U-shaped frame and a handle at one end, designed for cutting through materials such as plastic, steel, and other metals. It has small pins at each end of the frame that receive a blade, and a tensioner nut or knob is used to extend the length of the frame, which puts tension on the blade and locks it in place. Hacksaws can cut through metal pipes, rods, brackets, and other thin metals, as well as plastics such as PVC, PEX, or ABS on pipes or on sheet goods made of PVC, polystyrene, and more. They are typically used by plumbers to cut pipes and occasionally by electricians to cut conduit. Hacksaws are also used for jobs that require a more delicate touch than a reciprocating saw can provide.

In summary, a hacksaw is used for cutting through thin metals and plastics, and is commonly used by plumbers and electricians.