Green’s Dictionary of Slang

hang v.7

(orig. US) to turn a corner in a motorcar; as in hang a left, hang a right.

[US]Current Sl. I:1 2/1: Hang a left To turn left.
[US](con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 103: Stick shift, as in grind me a pound. Hang a left.
[US]J. Simon Sign of Fool 9: Hanging a right, we took Pine Street.
CBer’s Handy Atlas/Dictionary 27/2: hang a U - Make a U-turn. The verb ‘hang’ is also used for any turn, as in ‘hang a left.
[UK]A. Payne ‘You Need Hands’ in Minder [TV script] 51: The Cortina hangs a sudden right.
[US](con. 1970s) G. Pelecanos King Suckerman (1998) 230: He drove down to Newton, hung a right.
[US](con. 1986) G. Pelecanos Sweet Forever 11: Take this all the way down to U Street, hang a left.
[Aus]P. Temple Black Tide (2012) [ebook] When Mr Connors comes out of the carparfk, he hangs a U-turn and he’s off.
[UK]J. Hawes Dead Long Enough 218: This fucking big van spins out of some little lane in front of me and hangs a righter.
[US]G. Pelecanos Shame the Devil 11: Richard Farrow hotboxed his smoke while watching the black car hang a left.
[Aus]R.G. Barrett Mystery Bay Blues 251: Les hung a right and followed the road.

In phrases

hang a lilly (v.) [initial letters]

to turn left.

[US]G. Underwood ‘Razorback Sl.’ in AS L 1/2 60: Hang a Lilly at the next corner.
hang a ralph (v.) (also hang a roscoe) [initial letters]

to turn right.

[US]Coshocton Trib. (OH) 15 Mar. 4/4: Dear Helen: I thought you might like to hear one of the slang-things we read in your column has made it big at our school, but in a different way. You said ‘Hang a Roscoe’ or ‘Hang a Louie’ was ‘turn to the right’ or ‘left’ while you’re driving, as in ‘Hang a Roscoe at the clash’ (intersection).
[US]Current Sl. II:4 6: Hang a Ralph, v. To turn right.
[US]G. Underwood ‘Razorback Sl.’ in AS L 1/2 55: hang a Ralph ‘turn right’.
[US]Eble Campus Sl. Nov.