Green’s Dictionary of Slang

boards n.

[the material of which they are made]

[1920s+] playing cards; thus boardsman, one who runs a three-card trick game.

In phrases

toss the boards (v.) [1950s] (US Und.)

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

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

SE in slang uses

In phrases

off the boards (adv.)

[late 19C–1920s] (US) to excess, to a great extent.