Deadbolt.

I see it, I see the door, I hear the sound.

I picture a woman behind that door. A man locking it. The bolt clicking into place. The lock. Unopenable. Used for security, to keep people out. So who was the woman in the closet/room he’s locking in?

Maybe it would be better if the lock were on her side… and there was a secret passage to get her out. A passageway in the stone room. And the deadbolted door, once locked, the outside won’t see.