A: How do you like Jim?

    B: He’s a nice guy, but with some of the foolish things he does, I wonder if he’s not playing with a full deck.

    Note: This idiom refers to someone not mentally sound, crazy or mentally deranged. This is one of the many derogatory phrases that emerged in the 1980s which allude to someone “having a bit missing” or “not all there.” The implication is that the victim of the jocular insult lacks a portion of their brain. In this case the deck refers to a deck of cards. Anyone “not playing with a full deck” wouldn’t be expected to do well at cards.