That reminds me of some dodgy locks I encountered at university. There was a gap between the door and the frame, and if you slid a knife down here, it would unl

That reminds me of some dodgy locks I encountered at university. There was a gap between the door and the frame, and if you slid a knife down here, it would unlock the door (one of our tutors informed us of this, oddly enough). This was fixed by screwing a metal plate over the gap - of course, if you were determined enough, you could just unscrew the plate.