OK, I went on the Star Trek Cruise, and Neelix, or maybe it was the hl=olograph Doctor, told this joke:

So, an old man goes to his rabbi, to get advice on how to, um, satisfy, his wife. The rabbi gives him this advice, he comes back, it didn't work. He gives him that advice, he comes back, it didn't work.

So the rabbi says, get yourself a young man and a towel. You get on top of your wife, and while you are, um, attempting to satisfy her, the young man should wave the towel.

Next day the old man comes back, that didn't work either. OK, says the rabbi, switch places. The young man should get on your wife, and you wave the towel.

So that night the young man is on the wife, the old man is waving the towel, and the woman has a screaming, earth-shattering orgasm.

Afterwards the old man turns to the young man and says Sonny, now THAT's how you wave a towel!