Nails are something that we take for granted in this age of plenty that we live in, I remember my granddad sitting in the shop spending a rainy afternoon straightening used rusty nails some fifty years ago. He said we were lucky to have pails full of nails and would recount how at one time, when nails were made by hand, buildings would be purchased and demolished just to acquire the nails.

Now with modern manufacturing methods nails are a very minor factor in the cost of building a project, the only carry over from the old days is the "penny nail" size definition, which was the price per one hundred nails. This is abbreviated to "d", from the Roman coin Denarius, hence plans call for 3d nails ( pronounced 3 penny). Below is a chart giving the length in inches, and approximate number per pound of the most common sizes.

To convert sizes up to 10 d, take the length you want, subtract 1/2", then multiply by 4. For example a 2 1/2" long nail would work out to 2 1/2" - 1/2" is 2 X 4 equals 8 d, conversely divide size by four and add 1/2, so 6d divided by 4 is 1 1/2 plus 1/2 = 2"