A staple is a piece of metal wire bent into a "U" shape a top (or crown) and 2 "legs" (or shanks). The ends of the legs may be blunt, centrally pointed or have teeth (point at the side).
Some staples are flat rather than round and these have a width.
The total length of the wire in mm =
= (length of top in mm) + (2 * (length of legs in mm))
Most staples are described as a ratio X/Y where:
(1) X indicates the wire gauge (using the British Imperial Standard, also referred to as SWG)
(2) Y indicates the length of the "legs" in mm
Common wire gauges are:
(1) 26 (0.46 mm)
(2) 24 (0.56 mm)
(3) 23 (0.61 mm)
(4) 13 (2.34 mm)
The smaller the gauge the thicker the wire.
The length of the legs affect both:
(1) the number of sheets of paper that can be held together
(2) the fold over the holds the staple in place
number of sheets of paper that can be held =
= ((length of leg) - (length of foldover)) / (thickness of a sheet in mm)
