Bathroom door, door knob is 30+ years old, there are no screws showing, only the rose has a slot which a screwdriver will loosen so the rose rotates. Also a small hole which make no sense to me. How do I get this door knob off without destroying the door? I seem to remember the knob have to come off, then the rose, then the rest is easy but I cannot get the knob off. Someone must recall a small piece of magic (something sufficiently beyond my understanding) to do this. Thanks.