A motorist got a flat tire in front of an insane asylum. He took the wheel off, but when he stood up, he tripped over the hubcap containing the bolts, spilling them all down a sewer drain.
A patient looking through the fence suggested that the man take one bolt from the remaining three wheels to hold the fourth wheel in place until he could get to a service station.
The motorist, thanking him profusely, said, "Hey, that was a great idea! Why are you in this place anyway?"
The patient said, "I'm here for being crazy, not for being stupid."