Staple (fastener)

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A packet of staples commonly used in the home or office

Staples in use, showing the front and the back side. The back side shows the end flipped outwards on the left and inwards on the right

The Swallowtail Staples from Pasargadae - World's Oldest Staple - 6th c. BCE^{[citation needed]}

A staple is a type of two-pronged, usually metal fastener for joining or binding materials together. Small staples are used with a stapler to attach pieces of paper together while larger staples might be used with a hammer or staple gun for fencing, masonry, roofing and cardboard boxes.

Staples also find use in medicine for the closing of incisions and wounds, a function also performed by sutures.

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 materials butted together.
The crown of the staple can bridge 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 clinch the legs after they pass through the paper. Staples of this type were used on a desktop stapling machine, which was developed in 1877 and registered under US Patent No. 195,603. Modern 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. Many staplers have an anvil in the form of a "pinning" or "stapling" switch. This allows a choice between bending out or in. The outward bent staples are easier to remove and are for temporary fastening or "pinning". Most staplers are capable of stapling without the anvil to drive straight leg staples for tacking.

There are various types of staples for paper, including heavy-duty staples, designed for use on documents 20, 50, or over 100 pages thick. There are also speedpoint staples, which have slightly sharper points so they can go through paper easier.

Staple guns do not have backing anvils and are exclusively used for tacking and 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. Note: staple guns are not used in surgery.

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

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

Saddle stitch staplers, also known as "booklet staplers," feature a longer reach from the pivot point than general-purpose staplers and are used to bind pages into a booklet or "signature". Some, such as the Ring King, can also use "loop-staples" that enable the user to integrate folded matter into ring books and binders.

However, the staple in ancient times had different functions. They were used in masonry works, in which it was invented in ancient Iran in 6th century BCE during the reign of Cyrus the Great. These staple which is known as the "swallowtail staples", were used for tightening the stones together. Iranian architecture created this device for the construction of Pasargadae.

[edit] Specifications

The specifications for non-medical staples are described in ASTM F1667-05, Standard Specification for Driven Fasteners: Nails, Spikes, and Staples. A typical office staple is designated as F 1667 STFCC-04. ST indicates staple, FC indicates flat top crown, C indicates cohered (joined into a strip), and 04 is the dash number for a staple with a length of 0.250 inch, a leg thickness of 0.020 inch, a leg width of 0.030 inch, and a crown width of 0.500 inch.

Outside the United States, office staples are often described as 24/6 or 26/6, where the first number is the gauge of the wire, and the second number is the length of the shank (leg) in milimeters.