The size of a nail is measured in a unit known as
a penny. Penny is abbreviated with the lowercase
letter d. It indicates the length of the nail. A 6d
(6-penny) nail is 2-inches long. A 10d (10-penny) nail
is 3-inches long (figure 3-76). These measurements
apply to common, box, casing, and finish nails only.
Brads and small box nails are identified by their
actual length and gauge number.
A nail, whatever the type, should be at least
three times as long as the thickness of the wood it
is intended to hold. Two-thirds of the length of
the nail is driven into the other piece of wood for
The other one-third of the
length provides the necessary anchorage of the
piece being fastened. Protruding nails should be bent
over to prevent damage to materials and injury to
There are a few general rules to be followed in the
use of nails in building. Nails should be driven at an
angle slightly toward each other to improve their
holding power. You should be careful in placing nails
to provide the greatest holding power. Nails driven
with the grain do not hold as well as nails driven
across the grain. A few nails of proper type and size,
properly placed and properly driven, will hold better
than a great many driven close together. Nails can
generally be considered the cheapest and easiest
fasteners to be applied.
Figure 3-76.-Nail sizes given in penny (d) units.