Check it sticks are not consistent. A buddy had a fish that measured as an under on his check it board and measured over 16" on the tournament check it board. Tournament director even measured it as an under on my buddies board. Cost him over $9,000.
They have 2 different kinds, a thin one and a thick one. The thin ones have been known to bend causing inaccuracies. Buy the heavy duty one. I picked one up years ago after being told by a Game Warden that's the official measuring stick they use.