They hold our empire together as well.

The types of nails used in modern construction almost defy counting.

They include box nails, common nails, finishing nails, casing nails, brads and sprigs, to name a few.

Most countries quite intelligently use the metric system to describe nail sizes. For example, a "50 x 3.0" nail refers to a nail 50 mm long and 3 mm in diameter, with the lengths rounded to the nearest millimeter. Canada uses a similar system, except that nail lengths are given in inches.

But not the United States. Here, the length of a nail is designated by its "penny" size. This system began in England about the time carpenters were hammering stages together around Shakespeare's ears as he was furiously working on "Hamlet." In the U.S., we still walk into a store and ask for six-penny nails or 12-penny nails, with the size of the nail getting progressively larger.

Just why this is goes back to the Romans. D is a designation for denarius, a Roman coin sort of like a penny. In Elizabethan England, nails were sold by the pence, which adopted the "d" for shorthand because the Romans once invaded England and left behind a lot of nails along with their forts. Under this system, you could get 100 4d nails for 4 pence, 100 16d nails for 16 pence, 100 60d nails for 60 pence and so on.

Today in the U.S., the "d' refers to the length of the nail, prices having changed a bit. This incredibly confusing system remains.