The "penny" system for sizing nails originated in England. The letter "d" was the designation for the English
penny. In the early days, the same abbreviation was used to indicate a pound in weight. Nails were weighed by
the thousand, so if 1,000 nails totaled 2 pounds, they were 2d, or 2 penny nails. The penny system has endured,
althoughtoday it refers only to nail length. For example, a 2d nail is 1 inch long. Each higher number represents
an increase in length of 1/4 inch, up to 12d (3 1/4 inch long). After 12d, the penny system becomes more
irregular. Today, there are approximately 890 2d common nails (big heads) or 1.380 finishing nails (small
heads) per pound.