Have you ever gone to the hardware store for a pound of nails, only to be totally confused as to what you should buy? Knowing a little history should take the mystery out of the process.

Let’s start with nail size, because that is the least understood, but probably the most fun to talk about. If you were an English carpenter in the 1400′s, you went to the blacksmith for your nails, because hardware stores were still several hundred years in the future. For six pennies, you could get 100 – two inch nails. Of course, carpenters being pretty busy guys, shortened this by calling every two inch nail a six penny nail. Most of the carpenters of the day weren’t very well educated, either, so they further abbreviated it to 6d. Here, the symbol “d” is short for denarius, the name of an old Roman coin that looked nearly identical to the English penny.

So, when you visit your friendly neighborhood hardware store, you are going to find nails categorized in penny size, not in length. And, the shelf tag may actually say “3 penny” or “6 penny” or “9 penny” or it might just as well say 3d, 6d, or 9d, because the two terms are interchangeable.

So, we know that a 6 penny nail is 2 inches long. That means a 12 penny nail is 4 inches long – right? Wrong! Remember, it had to do with how much the blacksmith charged by the hundred count. There really is no rhyme nor reason for the relationship between penny size and and length, so simply find a chart and refer to it when you need nails. Besides the 6 penny nail that we now know is 2 inches long, another couple of examples would be a 2 penny nail, which is 1 inch long and a 10 penny nail, which is 3 inches long. See – no rhyme nor reason.

Now that you know you need a chart to convert the penny size to length, the next thing to master is nail types and their functions. There are literally dozens of nail types, such as box nails, brads, casing nails, common nails, finishing nails, joist hanger nails, ring shank nails, roofing nails, sinkers, all which you should find in a good hardware or building materials store.

Knowing which nail to use is critical to success on any project, so let’s examine the five most widely used: box, common, finishing, ring shank, and sinkers.

Box nails are for use in thin, dry wood. To reduce a nail’s tendency to split the wood, the point is slightly blunted, so that it crushes the wood fibers and punches its way through, instead of enlarging a crack.

Here’s one that uses itself in the definition. A common nail is a common construction wire nail with a head; common nails have larger shanks than box nails of the same size.

A finish nail is a wire nail that has a very tiny head, so it can be easily concealed. You conceal it by driving the head below the surface of the wood using a nail set.

A ring shank nail has small rings on the shank to prevent the nail from working back out over time and it’s often used to install sub-flooring.

Finally, a sinker has the same thin diameter as a box nail, it’s cement coated to hold it tight when driven, and it has a funnel shaped head to make it easier to nail flat. The head has a grid on the strike surface to keep the hammer from slipping. These are the most common nails used in the framing trades today.

The last important aspect of a nail is its finish. Basically, you will find “bright” and “galvanized” finishes. Bright nails have no coating and will rust easily, so they should be used in dry applications only, while galvanized nails are designed to be used out of doors. There are some specialty nails such as stainless steel and aluminum, but their use is usually called out as necessary by any project plans you might be working from.

So, just how long should the nail be that you use? Here’s a rule of thumb that seems to have withstood the test of time. You simply use as many pennies as there are 1/8ths of an inch in the wood you are nailing. So, to nail a 3/4″ face frame onto a cabinet, you would select a 6 penny bright finish nail, because 3/4 equals 6/8ths. To nail a 2×4, which is really only 1 1/2 inches thick, you would need to use a 12 penny nail, because 1 1/2 inches is 12/8ths.

The next time you visit your local “big box” store armed with all this information, rest assured you probably know more about nails than anyone else you are liable to encounter, including the department manager. Happy nailing!