A One-sided Blockage
Q J 9 5
K
J 8 4
A J 10 6 4
K 10 4 2
9 8 3 2
Q 7 6 5 3
—
6 3
7 5
A K 10 9
Q 8 5 3 2
A 8 7
A Q J 10 6 4
2
K 9 7
In this deal,
4 ♥ and
4 ♠ can only be made declared by South.
If North declares a major game, East can lead a club, ruffed, win a diamond return, and give West another ruff. Eventually,
the defense gets the spade king as well.
But
3 NT can only make when declared by North.
The secret here is that if West leads diamonds, the defense can successfully unblock the diamond suit. But if East
leads diamonds, the suit blocks, and the defense can only take four top tricks.