In the United States, the length of a nail is designated by its penny size, written with a number and the abbreviation d for penny; for example, 10d for a ten-penny nail. A larger number indicates a longer nail, shown in the table below. Nails under 1ΒΌ inch, often called brads, are sold mostly in small packages with only a length designation or with length and wire gauge designations; for example, 1 18 ga or 3/4 16 ga.
Nails are graded (measured) in a system that refers to their size. The unit is called a e"penny.p" The larger the number, the larger the nail. A 3-penny (3 d) nail is much smaller than a 16-penny nail. This system originated in 15th century England, when the m"penny " size determined what one paid a blacksmith to forge a hundred nails of that size of nail (one paid three pennies to get a hundred nails of the size called the l"3-pennyb" nail). This price became obsolete before 1500, but has continued to be so entrenched in convention, that its use persists to this day. Now we use it primarily as a measure of length (approximate, at least). We abbreviate the
