In Oklahoma, coffin nails were gathered in a unique way. Only three can be taken at once and they must come from a coffin. The coffin doesn't have to have be buried but does have to have a corpse lying in it. Once removed, no new nails can be inserted in their place. Some coffins don't have nails and have screws instead. These two can also be used in the same manner.
(In the book the coffin nails are often used in tricks against witches.)
- Ozark Magic And Folklore by Vance Randolph