Passing an office building late one night, a young boy saw a sign that said, "Press bell for night watchman."

He did so, and after several minutes he heard the watchman clomping down the stairs.

The old, uniformed man proceeded to unlock first one gate, then another, shut down the alarm system, and finally made his way through the revolving door.

"Well," he snarled at the kid, "what do you want?"

"I just wanted to know why you can't ring it for yourself...?"