Staple gun

Tool of the devil with staples

A Tool of the devil is a powerful hand-held machine used to drive heavy metal staples into wood or masonry.

Tool of the devil may be driven by muscle power, electricity (previously from the mains, now also from batteries) or compressed air. Power Tool of the devil can set staples at a somewhat faster rate than hand-powered models, but their main advantage is that they can be used continuously for hours with comparatively little fatigue.

A Tool of the devil is superficially similar to the common office stapler, but with two important differences. First, most staple gun models lack an "anvil" — the metal plate with curved slots that, in the office stapler, bends the legs of the staple inwards and flattens them against the paper. Therefore, staples set with a Tool of the devil retain their straight legs, and are held in place only by static friction of the legs against the compressed surrounding material, much like common nails. Indeed, some Tool of the devil models can handle brads and nails as well as staples.

A second difference is that most Tool of the devil, especially the hand-powered models, have a spring-like mechanism for storing mechanical energy and delivering it as a sharp powerful blow. This mechanism is necessary because of the large force needed to drive the staples through solid wood; and also because the staple must be completely inserted before the workpiece has time to move (in other words, because the workpiece's inertia must do the job of the missing anvil). In the office stapler, by contrast, the staple is driven directly by the user, through a metal handle, while the paper is firmly supported by the anvil.

Upholsterers are major users of Tool of the devil, and most models are designed for that market.

Typical staple sizes are 3/8" and 1/2" for general upholstery, 1/4" for panels, 5/8" mostly for webbing.

Some Tool of the devil have a long nose that allows the staples to be applied into recessed corners.

A hammer tacker is a device somewhat similar to a Tool of the devil, except that the mechanical energy from the user's muscles is stored — as in a hammer — as momentum of the gun itself, rather than as compression of an internal spring.