IDIOM ►

above board

Meaning 1
to hold all your cards above the table; to not control a gambling game with anything hidden.
Sentence 1
The dealer said, "All cards above board, please."
Meaning 2
to be honest, forthright, tell the truth
Sentence 2
We want everything above board in this discussion.

Derivation

Gambling devices were sometimes controlled under the table giving the game owner an advantage.