Why Do Construction Nails Have a 'd' at The End?

Nails have been holding things together for hundreds of years, but they're so ubiquitous that most of us never give them a thought. Nails are slowly being replaced by screws but it's unlikely nails will ever disappear completely, so in this article we'll dedicate a few paragraphs to the lowly common nail and take a look at why a nail size is called a penny, why nails have a 'd' at the end, and what denarius means.

What does the term 'penny' mean in nails?

The term 'penny' (plural pence) which is denoted with a small 'd' after the nail's size, can be traced to Old England where it was used to describe the price of a hundred nails. The size of the nails determined how many nails a buyer would receive for their money. One hundred 2-inch nails would cost six pennies (six pence in England), so the 2-inch nails eventually became known as six penny nails, written 6d. Eight penny nails are larger (2.5" long) so they cost more per hundred - eight pennies instead of six pennies. Here's a bit of nail trivia: back in the Days of Old, one hundred eight-penny nails cost eight pennies. In 2020, a one-pound box of eight-penny nails (which contains 105 nails) currently costs $4.25 at Home Depot.

The term 'penny' now denotes a nail's size, and that explains why nails have a letter at the end, but why do nails have a 'd' at the end, and not a 'p' for penny? For that answer we have to go back to the Romans. The 'd' at the end of the nail size is a leftover term from the old Roman 'penny' called the denarius.

What does denarius mean?

Long before cryptocurrency, the Romans used the term denarius (plural denarii) to denote the lowest value of the librae, solidi and denarii (pounds, shillings, and pence) currency denominations. The smallest denomination issued at the time was the 'as' (plural asses), but the as's value was only 1/10 of a denarius so asses weren't used as often to buy nails. The image below shows some old Roman coins:

old Roman denarius coins

The word denarius is derived from the Latin 'deni' (containing ten), and its value was originally 10 asses. In Roman days, 240 denarii were minted from one Roman libra (pound), so one pound (libra) contained 240 denarii. Before England moved to a decimal system in 1971, a penny was worth 1/240 of an English pound sterling, and its symbol was d, from the Roman denarius. To this day, the 'd' still remains attached to the nail size, and that's why nail sizes have a 'd' instead of a 'p' at the end.