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

She did so, and after several minutes she heard the watchman clomping down the stairs. The 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 her, "what do you want?"

"I just wanted to know why you can't ring the doorbell for yourself?"