They decide to go to the doctor to see what can be done to make their sex life more pleasurable.  The doctor listens to their story, and makes the following suggestion:

“Hire an attractive young man.  While the two of you are making love, have the young man wave a towel over you.  That will help her fantasize and should bring on an orgasm.”

They are a bit taken aback by the doctor’s words, but they are determined to succeed in their mission.

They go home and follow the doctor’s advice:  They hire a handsome young man and he waves a towel over them as they make love.

But it doesn’t help and she is still unsatisfied.

Perplexed, they go back to the doctor.

“Okay George,” says the doctor, “let’s try it reversed – have the young man make love to your wife while you wave the towel over them.”

Once again, they follow the doctor’s advice.

The attractive young man gets into bed with the wife and the husband vigorously waves the towel.  The young man gets to work with great enthusiasm and the wife soon has an enormous, room-shaking, screaming orgasm.

George smiles, looks at the young man and says to him triumphantly,

“You see, now THAT’S how you wave a towel!”