Dead As A Doornail
“This expression can be traced back to 1350, but could be even older. In the days before screws were commonly used in carpentry, nails secured one piece of wood to another. Unlike screws however, nails could often loosen over a period of time. To prevent this, it became common practice, particularly on large medieval doors, that when a nail was hammered through the wood it would be flattened or clinched on the inside. The process of flattening the nail would mean that the nail would be ‘dead’ as it couldn’t be used again.”
When you go in a pub with no atmosphere it’s said to be dead as a door nail.