A man wakes up one morning to find a gorilla on his roof. So he looks in the yellow pages and sure enough, there is an ad for "Gorilla Removers". He calls the number, and the gorilla remover says he can be over in 30 minutes.
The gorilla remover arrives and gets out of his van. He's got a ladder, a baseball bat, a shotgun and a mean old pit bull. "What are you going to do?", asked the homeowner. "I'm going to put this ladder up against the roof, then I'm going to go on the roof and knock the gorilla of the roof with the baseball bat. When the gorilla falls off the roof, the pit bull is trained to grab is testicles and not let go. The gorilla will then be subdued enough for me to get him in the back of the van."
He hands the shotgun to the homeowner. "What's the shotgun for?", asked the homeowner.
"If the gorilla knocks me off, shoot the dog!"