Two men working in a factory were talking. "I know how to get some time off," said one.

"How are you going to do that?"

"Watch," he said, and climbed up on a rafter. The foreman asked what he was doing up there, and the man replied. "I'm a light-bulb."

"I think you need some time off," the foreman said, and the first man walked out of the factory. After a moment, the second man followed him.

"Where do you think you're going?" the foreman shouted.

"I can't work in the dark," he said.