Two guys in a lunatic asylum decided to escape. They didn’t like each other very much, but they figured their chances would be better if they worked together.
On the night of their departure, they bypassed several security obstacles and stealthily made their way to the rooftop. All that remained was to jump across to the building next door.
The first inmate jumped across easily, but the second inmate had a bad knee and was afraid to make the leap.
“Hey, I’ve got an idea!” said the first inmate. “I’ve got a flashlight. I’ll shine it across to your building and you can walk across on the beam.”
“What, do you think I’m crazy or something?” said the second inmate. “I’d get halfway across, and you’d turn off the light!”