ace in the hole

Ace in the hole is a cliche referring to something that can supply a for sure victory when it is revealed, such as a tip, trick or hint. Ace in the hole originated from the game of poker whereas a card would be dealt face down and is kept hidden, this is called a hole card; the most propitious card is the ace. Ace in the hole is most commonly used when describing the fact that you have found a way to be sure of the end result.