If you are declarer at 3NT, what would you rather have to operate with: 13 points in your hand opposite 13 in dummy, or 26 in your
hand and none across the table?
It’s better to have high cards in each hand so you have entries to lead toward the high cards in the other. The defenders, for their part, strive to make declarer’s entry situation less fluid.
At today’s 3NT, South has 16 points opposite nine. He also has a good five-card suit to work with, promising spot cards and some honors in combination. Moreover, he gets a favorable opening lead: a heart to his A-Q. Would you back declarer or the defense?
South takes the queen of hearts and leads a diamond to the king. If East wins and returns a heart, South wins and leads a second diamond to dummy’s ten. East produces the jack, and the defense can take two heart tricks, but declarer wins a club shift, finesses in spades and takes the rest, making three.
Now let the defenders focus on declarer’s entry situation: East ducks the first diamond. If declarer comes back to a high club and leads a second diamond to the queen, East takes the ace. A heart return won’t beat the contract — declarer can win and still use the diamonds — but East instead shifts to the nine of spades. If South plays the queen, West’s king covers. Dummy’s entry to the long diamonds is dislodged, and South can take only eight tricks.
On defense, you have two ways to beat 3NT. If you can’t set up and cash five tricks in a hurry, you will still succeed if you stop declarer from taking nine.