Physical weakness
The little sexy housewife was built so well that the TV repairman couldn't keep his eyes off of her. Every time she came in the room, he'd jerk his neck right out of joint looking at her.
When he'd finished she paid him and said, "I'm going to make a..well ..unusual request. But you have to first promise me you'll keep it a secret."
The repairman quickly agreed and she went on. "Well, it's kind of embarrassing to talk about, but while my husband is a kind, decent man-- sigh -- he has a certain physical weakness. A certain disability. Now, I'm a woman and you're a man . . . "
The repairman could hardly speak, "Yes; yes!"
"And since I've been wanting to ever since you came in the door..."
"Yes; yes!"
"Would you help me move the refrigerator?"