open and aboveboard

Fully visible to public scrutiny; completely and openly honest or legitimate. Though some regulators have expressed concern over the merger of the two multinationals, everything about the deal has been open and aboveboard.

Also, honest and aboveboard. Candid and fair, without deceit or trickery, as in I'll join you, but only if everything remains open and aboveboard. Both versions of this expression are redundancies, since they use open and aboveboard in the sense of "honest." The latter word, dating from the early 1600s, comes from gambling and alludes to the fact that card players who do not keep their hands on the table (board) may be suspected of changing their cards under the table.

Honest and fair. This term comes from the rule that players, when dealing cards, must keep their hands above the board (i.e., table). Presumably when they put their hands under the table they could be changing their own cards. The expression appeared in print as early as 1608, in Joseph Hall’s Virtues and Vices: “All his dealings are square, and aboue the board.” It has been so used ever since.