tradesman’s (entrance), n. — Green’s Dictionary of Slang

tradesman’s (entrance) n.

[a pun on back passage]

the anus; thus go in by/up the tradesman’s, to have anal intercourse.

1993		I. Welsh Trainspotting 258: When I got bored fucking your old girlfriend, I decided I’d give wee Kev one up his . . . eh . . . tradesman’s entrance.
2002		D. Shaw ‘Dead Beard’ at www.asstr.org 🌐 ‘Right, Harry, give it her right up her Gary Glitter,’ Monica says and Dionne wails when she hears I’m coming knocking on her tradesman’s entrance.
2007		W. Ellis Crooked Little Vein 198: The old gentleman [...] preferred to take his pleasure through the tradesman’s entrance.
2024		J. Meades Empty Wigs (t/s) 337: Thank god you didn’t need to go to Eton to get buggered enough to widen the tradesman’s entrance.

In phrases

he doesn’t mind if he uses the front door or the tradesman’s entrance

a phr. used to denote someone who is bisexual.

1999

G. Seal Lingo 115: Non-heterosexual practices also feature in the broader Lingo, as in sayings like he doesn’t mind whether he uses the front door or the tradesman’s entrance (said of a bisexual).