These ugly square nails see to be made of black iron, but are exceedingly hard.

When hammered into any material, it will be as if hammering into wood. The nail will remain firmly in place and a word must be spoken to release the nail from its new home. This word was once carved into the head, but countless hammer blows have distorted it.

The user must make an Int check with DC of 15 to decipher the text.

Each nail has a different release word, all in Dwarvish.