Agricultural Tools Practice Test

The size of nails is expressed using the penny system, a historic unit that denotes length. In carpentry, nails are described by a number followed by a “d” (the penny), and a higher penny means a longer nail. This naming convention comes from old English trade, where the price per hundred nails influenced the sizing, and it’s still used today to indicate how long a nail will be. Gauge, by contrast, refers to thickness, not length, and inches or feet are general length units but not the standard nail-size designation. So the unit used for nails is the penny.