A double-headed nail, or duplex head nail, is the nail of choice for quick projects such as construction scaffolding, form work or temporary braces. Double-headed nails are as strong as common nails but feature two heads for easy removal. The nail is driven into the wood to the first head, leaving a small bit of the nail and the second head sticking out. All you need is the reverse end of a claw hammer to remove a double-headed nail.
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Double-headed nails were once known as scaffolding nails because they were the nail of choice for easy-to-disassemble, temporary wood scaffolding. When wood scaffolding was replaced by metal, the names double-headed nail and duplex nail became the common terms.
Double-headed nails are often used for temporary projects because they can be easily removed with a standard hammer. In concrete pouring projects, double-headed nails are used to fasten wood forms while the concrete is poured. Once the concrete has hardened, the wood forms can be easily taken apart with a hammer, yanking the nails out by the protruding second head of each nail. The double-headed nails are reclaimed in a similar manner when wooden scaffolding projects are completed.
According to federal specifications, a double-headed nail must be made of steel wire with a bright finish, round smooth shank, flat heads and a diamond point. Double-headed nails are the only nails that have two heads, which is their most distinctive feature.
Double-sided nails come in six sizes (6d, 8d, 10d, 16d, 20d and 30d) that range from 1 to 4 inches in length. The distance between each nail head ranges from 1/4 inch to 7/16 inch and increases in length as the nail's overall length increases. The diameter range of a double-headed nail ranges from .113 to .207 inches.
When hammering a double-headed nail, drive the nail into the wood like a regular nail, or up to the first head. The second head will remain visible outside the wood. To remove the nail, insert the reverse end of the standard claw hammer between the two heads. Pull the hammer toward you in a downward motion to release the nail from the wood.