Duplex head nails, also called scaffolding nails, get their name from the two layers on the head of the nail. This keeps the nail
from being driven completely into a surface. This may seem odd, but not if you want to pull the nail back out again in the near
future. When scaffolds are assembled, it is not usually supposed to be permanent, so these nails are often used and reused. Forms
for foundations and temporary hurricane barriers over windows are other common uses for duplex nails.