Cards speak
The rule that at showdown the actual value of the tabled cards determines the winner, regardless of what a player says they have. If you misread your hand but turn it face up, the dealer awards the pot correctly.
Frequently asked questions
What does cards speak mean in poker?
That the actual cards decide the pot, not the player's description of them. If you table your hand and misread it, the dealer awards the pot according to what is there — a player who says 'just a pair' while holding a straight still wins.
What does cards speak not protect?
Cards already in the muck. The rule only applies to a hand tabled face up at showdown. It also does not excuse a misdeclaration intended to mislead — deliberately announcing a hand you do not have, to make an opponent muck, can draw a penalty.
Should you rely on it?
Table your hand face up and let the dealer read it — that is exactly what the rule is for. But confirm the pot is pushed correctly before the cards are collected, because once the hand is cleared, correcting an error becomes a floor decision rather than a right.