Odd/Even Discards (aka Roman Discards) are a type of signal for attitude and suit preference. The first discard of a spot card has the following meanings:
- An odd spot card (9, 7, 5, 3) encourages that suit.
- A high even spot card discourages that suit, and is a suit-preference signal for the higher side suit.
- A low even spot card discourages that suit, and is a suit-preference signal for the lower side suit.
Against South's 3NT contract, partner leads the 2:
Dummy plays low, you contribute the 7, and declarer wins the ace. Declarer now leads a club to dummy's K, continues with the Q, and then the J. What do you discard?
Playing standard methods, discarding the 2 would discourage hearts but wouldn't encourage partner to lead a spade if he gets in. If you discard the 8 instead, this is a muddy-looking card that may be difficult for partner to decipher. Lastly, discarding the T would encourage spades, but likely wastes a spade trick.
Playing odd-even discards, you can discard the 8. This being a high even card, it discourages hearts while simultaneously indicating a preference for spades, the higher remaining suit.
Partner in fact has been holding up the A to see your discard. Once he wins the trick, he can switch to a spade to defeat the contract. The full deal:
- Odd-even discards are only used at a defender's FIRST discarding opportunity. This is actually an ACBL rule if you play in the United States.
- Odd-even discards always tend to encourage a particular suit. Discarding an odd card encourages that suit. Discarding an even spot card implies suit-preference for another suit. This is problematic when you don't necessarily want to encourage any suit. Playing standard discards, you can simply chuck a low spot card to discourage that suit without encouraging another one. But playing odd-even discards, any discard you make tends to encourage a particular suit, whether you want to or not.
- Some players also use odd-even signals in attitude situations. However, the risk of holding the "incorrect" pip cards increases, since you often have a limited set of cards to follow suit with (e.g. a tripleton).