An elderly couple were on their front porch in their rocking chairs. Out of no where, the wife hauls off and slugs her husband in the arm.

"Owe!! What the hell was that for?!" shouts the husband.

"That was for 50 years of terrible sex!!" answers the wife.

A few minutes of silence goes by and they resume rocking in their chairs. All of a sudden the husband hauls off and slugs his wife in the arm, nearly knocking her out of her chair.

"Ouch! What was that for??!" cries the wife.

"That's for knowing the difference!!" answers the husband.