The idiom “dead as a doornail” dates back to the 1300s, and was used by William Shakespeare in the 1500s and by Charles Dickens in A Christmas Carol in 1843. In use, the phrase means that something is, “not alive, truly unequivocally deceased.” But where does the phrase come from? To answer that question, the video below takes a look at the history of carpentry. When nails had to be made by hand, they were a valued commodity, and often had a lifespan much longer than the thing they were used to build. The video notes stories of houses being burned down, just to recover the nails that were used in their construction. In building doors, however, nails were used in a way that ensured that this would be the last project in which they would ever be used, hence the phrase.