Why are nails measured in "pennies"? And what's the "d" in a 16d nail mean?
I am puzzled by references to "penny" sizes for nails. How many "pennies" in an inch?
— Doug , Ormskirk, Lancashire, England
Steve Thomas replies : The "penny" system was a traditional way of sizing nails. The larger the number, the larger the nail. Penny designations originated in fifteenth-century England; the abbreviation "d" — from Rome's penny, the denarius — meant penny or pence. But the derivation of the system is unclear. One explanation — that so many nails could be purchased for a penny — seems wrong; that means 60d spikes would be cheaper than 2d (1-inch) brads. D may have indicated the price per 100 nails of a given length, thus relating cost to size. But it could also have been the price per pound. Unfortunately, neither explanation clarifies why box nails are shorter than common nails of the same penny or why the increment of length is inconsistent.
Of course, with the popularity of nail guns, both gas and pneumatic, these questions are becoming moot. Nails are increasingly sized by length — whether inches or millimeters — and packaged in clips or strips that can be slid into nail guns. These days it's not uncommon for a contractor to reach into his toolbox for a loose nail and come up empty handed.