As dead as a door-nail.

The comparison stresses that a person or animal is dead. It makes a plain statement of death more emphatic by likening the subject to an inanimate object.

The door-nail adds force to the description, not information about how or when the death occurred. The point is the complete absence of life.

If an emphatic description of death is wanted, this comparison gives the statement more force than simply saying “dead.” Its blunt imagery may be a poor fit for a sensitive conversation about a person’s death.