Adjective
dead as a doorknob
(simile) Entirely, unquestionably or certainly dead.
I tried the flashlight, but the battery was as dead as a doorknob.
I found the mouse who lived in our wall, lying on his back with his feet in the air—as dead as a doorknob.
John: [S]piritually, you're as dead as a doorknob and heading straight for hell!. Jack T. Chick