VIII.    PROXY SUITS

A prism signaler normally uses the trump suit to convey information about parity and identity of the single suit. At no trump, the defenders may agree to designate declarer's trick source as a proxy trump suit.

Consider this grand warm-up featuring powerful spades and a Minor Prism:

Declarer wins the diamond king opening lead with the ace. Next come the spade ace, a spade to the king, and a top spade. Declarer discards a diamond on the third round. West started with four (even) spades. West follows 4-5-2-9 in the proxy suit, to announce an odd single suit 4_5...2- clubs .

East must unguard clubs or hearts when spades are continued from dummy:

The Gerber sequence promised two aces and a king with declarer. The weak no trump allows for the club queen or the heart queen, not both. Which? Not the club queen. With it, three rounds of clubs would precede the spade avalanche to activate potential squeezes.

So declarer is 2=4=3=4 with the king-queen fourth threat in  hearts. East abandons clubs, holds hearts, and defeats the grabby grand.

The full deal:

In a variation of the same deal, South and West trade round threes. Declarer wins the diamond ace and runs spades. West, holding four (even) spades, follows 2-4-5-9 in the proxy suit, announcing an odd single suit 2_4...5- hearts.

Again, East must commit in this position:

The weak no trump rules out five hearts (2=5=3=3). And West can defend single-handedly against five diamonds (2=3=5=3) by keeping the diamond queen and a round queen-third on the side.

But West cannot contribute to the defense when declarer's threat is in clubs (2=3=3=5.) So East keeps clubs, abandons hearts and defeats the grand.

The full deal:

Consider this no trump deal which features solid hearts, a  Black Prism and a prism signal- the distributionally correct  guide to effective  defense in a PC world:

West leads the diamond eight, East plays the five, declarer wins with the ten; and runs hearts. East has three (odd) hearts and follows 3-5-10, promising an odd single suit.

Declarer started with two diamonds and the king now stands alone. On the fourth heart, East discards a discouraging spade. Unable to defend against an end play if declarer has the club queen, West places that card with East. On the run of hearts West abandons clubs, reducing to:

A

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A

Q

9

6

2

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If declarer, always down one, tries to establish a spade trick before cashing the club ace...down two.

The full deal:

South and East trade minor suit fours- a trade which strengthens declarer's diamond king. As compensation, East gets declarer's spade queen in exchange for the spade ten. Rotisserie bridge.

Declarer again wins West's diamond lead with the ten and runs hearts. This time East follows 5-3-10 with his three (odd) hearts, promising an even single suit 5_3...10- spades.

Consider three variations of the six card position that the 'four triple three' notrump declarer may reach after discarding on the run of  hearts. With the lead in dummy, declarer needs two tricks: 

If Declarer's spade king and diamond king remain guarded, West must also hold two cards in each of those suits. And, West must hold two clubs, a second to protect against a strip of the suit thus ensuring possession of an all important exit card.  This defensive alignment works in variation iii as well.

In all three variations if declarer starts with the club ace from dummy, West plays the king. If declarer instead starts a low club from dummy, East must pounce with the queen and play spades.

In the first variation declarer with a known 3=3=3=4, reduces to two cards in each non-heart suit. Two tricks needed with the lead in dummy:

Declarer's best start is a spade from dummy. But mere ham-fisted trick-grabbing by the defense limits this "no threat" offense to the club ace. Spade to the king and ace; spade jack overtaken by the queen; then, the spade nine (diamond queen discard); any club out -down one.

A more potent offense, in which the 3=3=3=4 declarer hangs on to three spades, is still no match for a distributionally informed defense. Two tricks needed with the lead in dummy:

Declarer starts with a spade from dummy to the eight, ten and jack. If West cashes the spade ace immediately, a low club exit to dummy's ace allows declarer to end play West with a club off. And continuing the club king rather than a low club allows declarer to use East's club queen as a stepping-stone to the spade king.

So before playing the spade ace, West plays the club king. If dummy wins, declarer gets no more tricks. If declarer refuses the club king, West cashes the spade ace; then puts the dummy which now lacks a club exit on play.

A third offensive scheme featuring clubs with declarer rather than spades proves no match for prism signaling distribution trackers. Two tricks needed with the lead in dummy:

A spade from dummy, low, king, ace. Here, if West plays the club king, dummy wins and puts East on play with a club. And, the defense must surrender a trick. So, rather than play the club king, West can exit with the club deuce to defeat the contract.

Alternatively, after a spade to the king and ace, an immediate spade jack squeezes a club from declarer and the club king is once again effective. If East makes the  ham-fisted trick-grabbing overtake of the spade jack with the queen to cash the long spade, declarer and West discard diamonds. And, East must be careful to exit with the club queen to defeat the contract.

When there are three single suit candidates, identification requires ordered play of three spot cards. With only two single suit candidates, a simpler identification technique is available.