Green’s Dictionary of Slang

boards n.

[the material of which they are made]

playing cards; thus boardsman, one who runs a three-card trick game.

[NZ]N.Z. Truth 30 Nov. 2/3: It comes to my deal again and when I picks up the boards I reckon he’s mine.
[Aus]Townsville Daily Bulletin (Aus.) 14 June 13: Cards are alluded to as ‘boards’, and the rogues who practice the three-card trick are the ‘boardsmen’.
[UK]‘P.B. Yuill’ Hazell and the Three-card Trick (1977) 120: Easier than geein’ up the punters with boards, innit?
[UK](con. c.1900) A. Harding in Samuel East End Und. 37: His father and his uncle used to play the ‘Crown and Anchor’, going about with the boards.
[Aus]R. Aven-Bray Ridgey-Didge Oz Jack Lang 21: Boards Playing cards.

In phrases

toss the boards (v.) (US Und.)

1. to conduct a game of three-card monte.

[US]Goldin et al. DAUL 225/2: Toss the boards. To operate the swindle-game three-card monte.

2. to deal cards, esp. in a crooked or illegal manner.

[US](con. 1950s) D. Goines Whoreson 37: We both knew how to toss the boards.

SE in slang uses

In phrases

off the boards (adv.)

(US) to excess, to a great extent.

[US]H. Blossom Checkers 22: The ‘bookies’ are swipin’ it off the boards.
[US]C.L. Cullen More Ex-Tank Tales 129: It is perfectly legitimate for him to back a ringer right off the boards if [...] he needs the money badly.
[US]W.R. Burnett Little Caesar (1932) 18: It’s the damn newspapers. They play that crime stuff off the boards.