The idiom "card one's sleeves" means to have a secret plan that gives one an advantage. Alternatively, one could use the synonyms "ace up one's sleeve" or "trick up one's sleeve" to express the same meaning. Other similar expressions include "keep something in reserve,""hold something in hand," and "have something in the bag." These phrases convey the idea of holding onto a valuable resource or knowledge that can be used to one's advantage when needed. Whether you're a strategist, a negotiator, or a gambler, having a card up your sleeve is an important tool in achieving your goals.
