When a red 4 is face up, either by being dealt or by having a hole card exposed, the person holding the red 4 may make any person turn one of their board cards face down. For example, if Player A holding the X-X-6♠-4♣-Q♥ makes Player B expose one of his hole cards, and he exposes a 4♥, Player B can then make Player A turn down the 4♣ and Player A’s hand now cannot win at showdown.
