The advertised size of common nails is based on the ‘penny’ system, which was established centuries ago to indicate the cost of one hundred hand-forged nails. For instance, 100 two-penny nails cost 2 cents, 100 4-penny nails cost 4 cents and so on. Today, the ‘penny’ rating is used exclusively for identifying the nail length. The nails most often used in construction are 8, 10, 12, 16, and 20-penny, with the lengths ranging from 2½ inches up to 4 inches respectively. Incidentally, the symbol for ‘penny’ is a small ‘d’, which many believe is the abbreviation for the word denarius, the penny of ancient Rome.
