How long a nail should you use for a 1-inch board? Or a two-inch board, 8-penny or 16? The accepted rule of thumb is 2-1/2 times the thickness of the wood you are nailing through. Thus, for 1-inch- thick material, you would use an 8-penny nail and for 2-inch-thick material, a 16-penny nail. Nails sized by the "penny" system have a number and a small letter "d." To gauge how long a nail is, divide the size by four and add a half-inch. Thus a 12-penny nail is (12 divided by 4) that's three (plus one-half inch) -- three and one half inches long. If your work will be exposed to the elements or used in a very damp location, it'll weather better if you use galvanized nails (or better). And that's the On The House tip for today.