Green’s Dictionary of Slang

(N.Z. gay) as private flat where a male sex worker see clients.

2010

W. Ings ‘Trolling the Beat to Working the Soob’ in Int’l Jrnl Lexicog. 23:1 77: [T]he terms fuck flat, in-call, in-house, headquarters, HQ, and the officeto describe private residences from which [male sex workers] worked.