When it is use ace up your sleeves?

You use the term I have an "ace up my sleeve" when you have an extra advantage that your opponent is not aware of that may assist you to win. It is a term that is taken from the card game of Poker where the "Ace" card is the high card and, should a person be cheating at the card game, they may hide an Ace up their sleeve and play it in the game to win if they need it. The term "I have an Ace up my sleeve does not, like in the card game example, necessarily imply cheating though. It simply means that you have an additional advantage.