When on the road, I have a spare battery in my bag for my PowerBook G4. But being a modern person, I have no coins in my wallet anymore. This is a problem when I want to change the battery of my lapptop.
I tried unlocking the battery with a key, but that was not easy. Then I discovered that one of the corners of the spare battery can be used very well to unlock the other battery. No more coins for me. I don't know if this works for other *books as well.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2007102700000458