Hold the towel
"Hold the towel" is a phrase you use when you hold a towel for your buddy while he fucks a hot chick, and hand it to him after he is done so he can towel off after washing up. And while he cleans up, you fuck the hot chick.
Jon: Man, that girl is so hot!
Steve: Yeah! Shall I hold the towel for you?
Steve: Yeah! Shall I hold the towel for you?