dead as a doornail

Dead as a doornail is the phrase which means to be devoid of life, finished with, unusable and often dead. It is most commonly applied to inanimate objects which have no value of life as they have never lived with a beating heart, along with people, plants and animals that are devoid of life or who have been deceased. Doornails, as inanimate objects, are very dead in that they never lived which is where the cliche comes from.