Oh, this is great fun if you want to vomit your stomach out. If this trick is true, you can make an elevator go into free fall for five feet. It's not a lot, but it's a good kick.
According to this woman, you can do it thanks to a mechanical glitch in units made by a company called National Elevators. You first should call an elevator up, then block the doorway until you hear a nudge sound, get in and push down. The elevator will start going up and suddenly change its mind and free fall for five feet before slowing down.
If I were you, I wouldn't try to hack any elevators. But if you must, please tell us what you find. Or tell the emergency personel in the ambulance so they can tell us. [Doobybrain]