A after sexual intercourse activity - where you nut in a rag - commonly called a "nutrag" but in this situation your using a more custodial or shop rag type towel, after cumming in this towel you then slap it in your partner's face and tell them they've been hit by the "Janitor"
You have been at the club all evening and pick up a pretty descent bimbo for later in the evening festivities. Right after you've "gotten yours" because no one cares about hers, you quickly slap the cum filled "janitor" towel on her face. By accomplishing this you secure a quick and speedy "getaway" while she's in bathroom thinking what an asshole without the, "can I have your number?", "will I see you again soon?" questions.