# 10d Nail Length

Trivia Time at Hansen Pole Buildings

My children have often accused their father of knowing more worthless trivia than anyone else on the planet. Having stumbled across an occasional television game show, I have to say the title certainly long belongs to others than me. However from time to time I do know some weird stuff.

Hansen Pole Buildings Managing Partner, Eric, asked me how it is “d” got to be associated with “penny” as a measure of nails. In structural engineering “d” most often denotes the diameter of an object, rather than in the case of nails – where it is length.

In England, prior to about 1488, the penny size was the price in pennies of a hundred nails of a particular size. Adding to the confusion (keep in mind, in England weight is measured in stones, as an example), this hundred was what is known as a “great hundred” which is 120, not 100.

The penny system was already a convention before the time of Queen Elizabeth (1533-1603), as merchants’ records of the era recorded entries such as 100 4d nails for three pence, 300 3d nails for 7-1/2 pence, etc.

The size of a nail is not based upon its weight in pennyweights. A pennyweight being equal to 24 grains of well dried wheat gathered out of the middle of the ear. While three centuries ago this may have worked, in the modern world a pennyweight is 1/20th of a troy ounce. Troy ounces is a system of measuring precious metals. If you are into the metric system, one troy ounce equals 31.1034768 grams.

But where did the “d” come from? The denarius was an ancient Roman coin. Under Emperor Claudius, the Romans invaded the British Isles in 43 A.D. About 400 hundred years later, as their empire crumbled, the Roman occupation ended – leaving behind the “d” for denarius, which became associated over time with the old British penny.

As used today in the United States, a 2d nail is an inch long. Each one d increase is ¼” in length up to 10d nail (a three inch nail). This is followed by the 3-1/4” long 12d and the 3-1/2” length 16d. Larger sizes, beginning with 20d are all multiples of 10 and are each ½” longer than the size immediately before.

And now – you also can “win” if you are ever on a game show and asked “what does the “d” stand for in nails? Better yet, you can tell them a 10d nail is 3 inches long!

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