Can the play help your side?
Marie Curie said during a lecture at Vassar College, “(Scientific work) must be done for itself, for the beauty of science, and then there is always the chance that a scientific discovery may become, like radium, a benefit for humanity.”
At the bridge table, do not make plays that benefit only the opponents. In today’s deal, how should East defend against four spades after West leads the diamond five, and dummy covers with the nine?
South cue-bid two clubs to show a maximum pass. Then North bid aggressively in jumping to game opposite a partner who could not open the bidding.
When East covered dummy’s diamond nine with his king, South took the trick and played a spade to the nine. East won and gave his partner a diamond ruff, but declarer won the next trick with the club ace and ran the heart queen. When that held, South continued with a trump to the queen and ace, and took dummy’s two diamond winners, discarding his heart nine. Declarer lost one spade, one club and the diamond ruff.
East should have realized that his partner had led from either a singleton or a doubleton. So, covering dummy’s diamond nine with the king was pointless; it benefited only declarer, giving him four diamond winners immediately.
If East had played low, probably South would have won with his diamond 10 and taken the spade finesse. East would have won and given his partner a diamond ruff. Then West would have exited with the club king, and the contract would have failed if West did not cover the heart queen (the first of touching honors), but did cover if declarer continued with the heart jack.