A hacksaw is a fine-tooth saw with a blade

Blade

A blade is that portion of a tool, weapon, or machine with a cutting edge and/or a pointed tip that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials...

 under tension in a frame, used for cutting

Cutting

Cutting is the separation of a physical object, or a portion of a physical object, into two portions, through the application of an acutely directed force. An implement commonly used for cutting is the knife or in medical cases the scalpel...

 materials such as metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 or plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s. Hand-held hacksaws consist of a metal arch with a handle, usually a pistol grip

Pistol grip

On a firearm or other tool, the pistol grip is that portion of the mechanism that is held by the hand and orients the hand in a forward, vertical orientation, similar to the position one would take with a conventional pistol such as the M1911....

, with pins for attaching a narrow disposable blade. A screw or other mechanism is used to put the thin blade under tension. The blade can be mounted with the teeth facing toward or away from the handle, resulting in cutting action on either the push or pull stroke.