Green’s Dictionary of Slang

the act of masturbation.

1971		(con. WWII) B. Aldiss Soldier Erect 87: I know you’re a lusty young lad [...] but you’d do best to stick to the old hand-shandy.
1989		J. Morton Lowspeak.
1996		(con. 1970) G. Moxley Danti-Dan in McGuinness Dazzling Dark (1996) I v: Okay ... you gave him a hand shandy. You looked bored rigid.
1997		(con. 1960s) A. Frewin London Blues 67: Fellows go there to play pocket billiards, to have a hand shandy.
2002		www.upsideclown.com 18 Apr. 🌐 Every year in Britain alone tens of thousands resign themselves to solitary hand-shandy due to the persecution of Celtic physical attributes.
2005		L. Redhead Rubdown [ebook] What about massage, then? [...] all you gott to do is a bit of a rub, a bit of a tug. Hand shandy.