This article is from the Baby Proofing FAQ, by Sandra Smith, firstname.lastname@example.org with numerous contributions by others.
From: Glen Ecklund, Department of Computer Sciences, University of Wisconsin
Determine whether there are any rooms they can lock themselves into.
Ethan likes to lock himself in the bathroom. Fortunately, I was at my
desk when my wife called. She remembered that there was a gizmo to open
the bathroom door, but she didn't remember where it was. Also, fortunately
the toilet lid was locked. We started locking it as soon as he opened it
the first time. Now he plays with the lock, but he doesn't expect to
be able to open the lid, even when someone forgets to lock it.
Now I try to make sure that any sitter knows how to unlock the door. We
keep it shut normally. And when he stays at someone else's house I mention
the potential problem.
Our other bathroom door has a lock which we hadn't even noticed, since we
don't use it. There is no easy way to open it from the outside, so I'm
glad he didn't find it first. I disabled it by putting a screw partway
into the hole in the door jamb, so the deadbolt hits the screw and
cannot latch. The doorknob latch is separate, and unaffected.
A small tragedy happened Saturday when Ethan was with the sitter at a
conference at a hotel. He locked himself into the room, and locked the
sitter and another child out. She left him there and went down to them main
desk for help. I think he has recovered by now, but he certainly had
some extra crying to do for a while.
I keep thinking of new things. Watch out for wastebaskets! Ours is locked
away under the sink, but Ethan still managed to transfer a couple of spoons
from the dishwasher to it, which was lucky to notice while taking out
the trash. And Madeleine's keys are long gone. But we still have the
remote controls. :-)