I saw a bumper sticker today that said,
"Minds are like parachutes: They only work when they are open"
My first thought was, 'I've got something that will open your mind: My shutgun!'
I then surmised that the reason their mind is like a parachute is becaused its filled with air.
My mind, on the other hand, is like a steel trap. Not only because it traps useful information and holds onto it, but because when people try to put anything stupid in it chops off their hand.