In the early days of blacksmiths forging iron and steel, one of the products they made was nails. As you can imagine, making a handful of nails by hand, from iron ore, using an anvil, hammer and forge would make them tremendously expensive. Only the wealthy could afford nails for any use while common folks used made do with all- wood methods of construction such as post and beam with wooden pins, and mortise and tenon joins just as the Amish people do to this day.
What few nails were around were always re-used if at all possible, again due to their value. One of the more common uses for nails was in the construction of doors of larger houses; nails somewhat longer than the thickness of both pieces of wood to be joined were used and the protruding tip of the nail was hammered over on the inside of the door. This made a very strong and permanent construction method but also guaranteed that nails used in this way could never be used again. Perhaps part of this usage was so that the wealthy could flaunt their affluence amongst the common people. In any event, it did yield a great English expression which is commonly used to this very day: “Dead as a doornail” or “Deader than a doornail”, meaning something that is so completely used up or worn out that it cannot be used any further no matter how much effort is applied.
The roots of this expression are older than modern English; the expression was originally written in Middle English (11th to 15th century) and may possibly even pre- date that period.