An old man and woman were sittin' on the front porch.
All of a sudden, the woman reaches over and WHAM! Smacks the man up side the head.
Hurt and puzzled, the man asks,
"What was THAT for!"
"Fifty years of bad sex!" the old woman replied.
The man sits there a minute, pondering,
and pondering,
and pondering....
Then he reaches over and WHAM! Smacks HER upside the head while yelling--
"Well, THIS is for knowing the difference!"