The hanky code was a covert sartorial code used predominately by queer men in the 1970s and into the 1980s. Simply put, a bandana is worn in one’s back pocket for the purposes of sexual signaling.
Handkerchief code - Wikipedia
The Project Gutenberg eBook of History of the Australian Bushrangers, by George E. Boxall.
History of the Hanky Code and Its Significance in History
The Hanky Code 101: The History Behind Gay Flagging
PDF) All that glitters is gold: queering waste through campy craft
Hanky Code Introduction — ONYX NY NORTHEAST
Hanky Panky: An Abridged History of the Hanky Code
Red - Wikipedia
Listen to Q4Q: Queer Personals Podcast podcast
Hanky Panky: An Abridged History of the Hanky Code
Out of the Archives - Hanky Panky: The History and Cultural Impact of the Hanky Code