Staple (fastener)

A staple is a type of two-pronged, generally metal fastener for joining or binding materials together. Large staples are used in masonry and cardboard boxes, and are generally dispensed with a staple gun; smaller ones can attach pieces of paper to one another, and are dispensed with a stapler.

Staples have some advantages over other fasteners.

• Most kinds of staples are easier to produce than nails or screws.
• The crown of the staple can be used to bridge between two materials butted together.
• The crown of the staple can bridge over a piece and fasten it without puncturing with a leg on either side, e.g. fastening cable to wood framing.
• The crown of the staple provides greater surface area than other comparable fasteners. This is helpful with thinner materials.

The legs of a staple can be allowed to protrude out the back side and folded over to provide greater binding than the friction of straight legs. (Note: The term "stapling" is used for both fastening with straight or bent legs however when differentiating between the two the term "tacking" is used for straight leg stapling while the term "stapling" is used for bent leg stapling when being contrasted with "tacking".)

The most common staples are the ones used for paper. They are almost exclusively applied with a mechanical stapler which bend the legs after they pass through the paper. Staples for a paper stapler are made from bent wire and glued together to form a long strip of staples. The papers to be fastened are placed between the main body and the anvil. The papers are pinched between the body and the anvil then a drive blade pushes on the crown of the staple on the end of the staple strip. The staple breaks from the end of the strip and the legs of the staple are forced through the paper. As the legs hit the grooves in the anvil they are bent to hold the pages together. Most staplers have an anvil in the form of a pinning/stapling switch. This allows a choice between bending out or in. The outward bent staples are easier to remove and are for temporary fastening. Many staplers are capable of stapling without the anvil to drive straight leg staples for tacking.

Staple guns do not have anvils and are exclusively used for tacking. They typically have staples made from thicker metal. Some staple guns have round heads for fastening small cables, e.g. phone or cable TV, without damaging the cable.

Staples for larger cables are typically driven by hand with a hammer.

The large staples found on corrugated boxes have folded legs; however they are applied from the outside and do not use an anvil. Instead jaw like appendages push through the cardboard alongside the legs and bend them from the outside.

Saddle stitch staplers aka booklet staplers are used to bind pages into a booklet or signature.