In some older apartment buildings (eg, Portland, OR), the fire egress plan involves other residents being able to break into your apartment and exit using your

In some older apartment buildings (eg, Portland, OR), the fire egress plan involves other residents being able to break into your apartment and exit using your external fire escape. In these buildings, you'll see an apartment on each floor with a glass window in their door, and a heavy object hanging from a chain next to it. (It's a fun puzzle for guests -- "See that bolt hanging from the chain? See the adjustable crescent wrench on the next floor? How does that work?")