A dummy reversal is not your mistake instead of your partner’s. Last column, I defined a dummy reversal by words. It is described here by an example.
The Bidding: South opens one spade with a shapely 14 points and North makes a bid of two diamonds. North has spade support, but is stronger than a two spade (6 to 9 points) or a three spade (limit, 10-12) bid would indicate.
South rebids his four-card heart suit and North forces the auction with a temporizing bid of three clubs. It is forcing one round. North is too strong to jump to four spades (13 to 15 points). South raises clubs showing club support. North knows that South has five spades, four hearts and three or four clubs. Therefore South must have at most a singleton diamond. North places the contract in six.
The Opening Lead: West leads the ten of diamonds. One needs a safe lead against a slam and top of nothing from a long suit usually will not give declarer long suit tricks.
Requirements for a Dummy Reversal:
a. High Trump
b. 3-2 break
c. Long trump hand ruffs
d. Enough transportation
South wins the opening lead with the ace of diamonds and cashes the queen and ten of spades, following with the six and five, to see that the split is three-two. He now knows he has all the requirements for a dummy reversal.
He ruffs a diamond with the ace of spades, goes back to dummy with the ace of clubs, ruffs another diamond with the king of spades, goes back to dummy with the ace of hearts, ruffs the last diamond with the jack of spades and returns to dummy with the king of hearts.
South has no more spades and North draws the last trump with the 9 pitching a losing club from South to make an overtrick at six spades.
-When declarer cashes the queen and ten of spades and finds a bad trump split, he will abort the dummy reversal, draw trump and lose one club making six spades exactly.
-If dummy had less entries, declarer would use trump as transportation and would not be able to check for a good trump break. In this line of play, he would go down with a four-one trump break. Missing five cards will break three-two 68 per cent of the time.
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