Generally, when cards are declared wild, all cards of a certain rank are wild. For example, in the game of Baseball, all 9's are wild, regardless of what suit they are. On occasion, however, a specific card can be called wild (e.g. "The king of hearts is wild"), or a specific set of cards (e.g. "One eyed jacks are wild").
Wild cards are not, in general, used in live casinos or even online casinos (though some casinos use a bug for some games, which is similar to a wild card). They are frequently used, however, in home games, where oftentimes players are playing Dealer's Choice and wild cards are being declared at the start of each new game round.
There are two ways to play wild cards:
- No Duplication
Wild cards can be treated as though they were any other card, except for a card which is already in the hand with the wild card. This prevents "impossible" poker hands from occurring, such as "five of a kind". If a hand already has all four queens in it, a wild card cannot be another queen. Note that a wild card may duplicate a card which is in another player's hand.
- Anything Goes
Wild cards can be any valid card in the deck, even a card which is already in the hand in question. This allows hands like "five of a kind" to occur.
As you might imagine, it is a good idea to select one of these ground rules before playing a game with wild cards, or some ugly disagreements can result.
Jokers, if they are used in a poker game, are more often used as a bug than as a wild card, but they can be declared wild if the players so desire.