A traveling salesman whose car has broken down goes to the door of the closest farmhouse. The farmer says, "You can spend the night but you'll have to share a room with my beautiful daughter."
"Oh, I don't mind that," exclaims the salesman.
"Just one thing," says the farmer. "No funny business."
"Oh no sir," says the salesman. "You can count on me."
Just to be safe, the farmer builds a wall of eggs between the two beds in the daughter's room. In the middle of the night, the salesman can no longer control himself, busts through the eggs and has his way with the farmer's daughter.
They take the rest of the night piecing the eggs back together one by one and rebuilding the wall.
The next morning, the farmer goes to his daughter's room and takes a couple eggs to the kitchen to make breakfast. Cracking open the first egg, of course, produces nothing. Cracking open the second egg, likewise.
The farmer pokes his head out the window and yells, "OK, which one of you roosters is using a rubber?"