Nailer

The d is a penny, and it only means a length

The d in 16d is a penny — an abbreviation of the Roman denarius that reached the hardware aisle by way of what a hundred nails once cost. It says nothing about the nail except by convention, so 16d is simply the name of a three-and-a-half-inch nail.

There is a formula people quote — penny divided by four, plus half an inch — and it is exactly right from 2d to 10d and then breaks. It predicts three and a half inches for a 12d, and a 12d is three and a quarter. Above 10d the table is the authority.

Common, box and finish are three different wires

At the same length the three families differ in shank diameter, and that difference is the whole reason they exist. A common is the thickest and is what a nailing schedule assumes. A box nail is thinner, holds less and splits less, which is the trade you want near the end of a board. A finish nail is thinner again with a head barely wider than the shank, so it sets below the surface and fills.

Substituting a box nail where commons were specified quietly reduces the connection, because the schedule was written around that diameter. Finish nails are trim fasteners and carry nothing structural — there is no head for the wood to bear against.

Gauges, for the smaller guns

Trim nailers are sold by wire gauge rather than by penny, and the number runs backwards — a bigger gauge is a thinner nail. A 15- or 16-gauge finish nailer is for casing, baseboard and door jambs; an 18-gauge brad nailer is for small trim and holding parts while glue dries; a 23-gauge pinner leaves a hole you genuinely have to hunt for and holds almost nothing on its own.

That last one is the point of it. A pinner is a clamp you can fire, for mitre returns and small mouldings where a brad would split the piece and a clamp will not reach.

How many a sheet takes

Sheathing and subfloor are fastened on an edge-and-field pattern: closer along the edges, where a panel is most likely to lift, and wider through the middle. Six inches at the edges and twelve in the field is a common schedule, and the count for one sheet is higher than most people estimate.

Note the perimeter is one loop rather than four edges — adding up four edges separately double-counts every corner.

What this page does not tell you

• —Nailing schedules are set by the building code and by the engineer for the job, and the 6"/12" pattern above is only a common example. Ring the building department for what your jurisdiction has adopted, and follow the plans where they differ.
• —Coating matters as much as size. Bright nails rust; anything outdoors or in treated lumber wants hot-dipped galvanised or stainless, and treated lumber is corrosive enough to eat an electroplated nail.
• —Count-per-pound is derived from the shank volume and the density of steel, which lands on the published counts because the head and point roughly cancel. Real boxes vary by maker and by coating.