The Brennholt Institute of Applied Taxonomy records a paper fastener, the brass split-legged pin often called a Parisienne or a brad, by shank length and head diameter: shanks run from 12 mm (about ½ in) to 50 mm (2 in) in the common range, and heads are 7 mm to 12 mm across. The Institute has found no published standard for either figure, and the sizes below are its own measurements of retail stock.
The shank is the part that passes through the paper, and its legs are opened flat on the far side. The head is the round cap on the near side. The Institute measures the shank from the underside of the head to the end of the legs, before they are opened.
The Institute examined 260 fasteners from 19 retail packs in 2025. They fell into five shank lengths, which the Institute finds are the sizes sold in practice.
| Shank length (mm) | Shank length (in) | Head diameter, mean (mm) | Pins in sample |
|---|---|---|---|
| 12 | ½ | 7.4 | 34 |
| 19 | ¾ | 8.6 | 71 |
| 25 | 1 | 9.8 | 82 |
| 38 | 1½ | 10.7 | 49 |
| 50 | 2 | 11.6 | 24 |
The shank length is a round figure in inches in every case. The Institute reads this as evidence that the sizes descend from an inch-based trade, even in packs labelled in millimetres.
The Institute proposes a four-part class for fasteners, in which the first element is the shank length class and the second is the leg count. It is the Institute's scheme, not a trade standard.
A rule of thumb sets the shank length at the stack thickness plus 10 mm, enough for the legs to be opened. For paper of 80 gsm, a stack of 100 sheets is about 10 mm thick, so a 25 mm shank is adequate. The Institute offers this as a working guide only.
Most fasteners in the sample were brass-plated steel; 22 were solid brass, and 11 were aluminium. All had two legs, with a split between them. A few suppliers list three-leg and four-leg versions, none of which appeared in the Institute's sample. The Institute does not rank the materials, and discusses the plating of steel on its page on galvanising and plating. The wire gauges of the legs vary, and the Institute's discussion of gauge is on the wire gauge page.
The fastener has a long record of use in offices, and the Institute makes no claim on its invention. Several histories attribute the name Parisienne to French origin, and the Institute has found no dated source it would rely on. It cites none and offers no date.
The Institute's panel disagrees on the best measure of size. A majority use shank length, since it controls how many sheets the fastener will hold. A minority hold that head diameter is the better measure, since it controls whether the fastener pulls through paper. The Institute records both in the table and ranks the shank length first.
A larger head resists tearing through softer paper. Where a binding other than a fastener is wanted, the Institute's page on treasury tags deals with the usual alternative, and the page on staples with another.