This type of deal, popular with bridge problemists, features a play that is often missed at the table. A defender ignores “Second Hand Plays Low” in order to protect partner’s entry
West led his fourth highest spade against 3NT. (It is tempting to lead the jack, but you need partner to have at least one high spade, and this is a variation on “high” cards from the shorter hand first’.) East played a Third Hand High queen of spades, and declarer correctly ducked – he must establish clubs for his contract, and will have to give up the lead twice. East returned a spade to the ace. Declarer crossed to the jack of diamonds and led a club from the table.
An unthinking Second Hand Low lets the contract through. West might duck the first round of clubs, but he has to win the second, and though he can clear spades his entry has gone. Declarer makes two spades, two hearts, three diamonds and three clubs, ten tricks in all. To beat 3NT East must win the first club with the king and clear spades. Now West’s ace is an entry to cash two long spades and defeat the game.
How does East know that West has the ace of clubs? He does not know for sure, but this is his best chance of defeating the contract. If South has the ace of clubs the game will surely make – he can establish at least four club tricks to go with two spades and three diamonds.