The Artificial Insemination Man
 

Amy, a blonde city girl, marries a farmer.
One morning, before he goes out to the fields, the farmer says to her,
"The Artificial Insemination man is coming to impregnate one of our cows
today.
I drove a nail into the two-by-four above the cow's stall. You show him
where it is, okay?"
So the farmer leaves for the fields, and a while later, The Artificial
Insemination man arrives.
Amy takes him down the long row of cows until
she sees the nail, and tells him, "This is the one. This one right here!"
Terribly impressed by what seemed to be such a dizzy blonde, the man
asks, "How did you know this is the cow to be bred?"
"By the nail over it's stall," Amy explains.
Then the man ask, "What's the nail for?" !
"I guess it's to hang your pants on."

This is also referred to as "Stump Breaking" in hillbilly speak. I'm originally from the Ozarks, I can talk. :D