An elderly couple
An elderly couple was sitting on there rocking chairs rocking back and forth.
When the woman whacked her husband as hard as she could right off his chair.
Surprised and disorientated he said: "now why did you do that?" and she replied: "That is for 50 years of horrible sex".
So he sits back down and thinks about it for a while, and pretty soon you hear another whack, this time the wife falls off the chair and soon, gets back up and says "what was that for?”
He replied, "that is for knowing the difference."