You open 1and partner responds 2NT (game-forcing raise). You have confidence in your Blackwood methods and leap to 4NT, Roman key card Blackwood (1430).
When you find you are missing one key card, you check to make sure you are not missing the Q as well. Partner says he has it so you merrily bid 6. West leads the 10. Now what?
Solution:
The full deal:
K Q J 9 6 5
K J 3
4 3
7 5
2
10 9 8 7
K J 9 7
Q 8 6 4
3
5 4
10 8 6 5 2
A J 9 3 2
A 10 8 7 4
A Q 6 2
A Q
K 10
The idea here is to take two chances by first leading up to the K, and if that loses, taking the diamond finesse. Before leading up to the K, win the heart lead in dummy, draw trumps, play three more rounds of hearts discarding a club from dummy, cross to dummy with a trump and lead a club.
If East has the ace, your troubles are over as you can pitch a diamond from dummy on the K (East will surely take the ace if he has it). If the king loses to the ace, there is still the diamond finesse.
One of two finesses (75%) makes this a good slam. In many cases, a good way of keeping alive when two finesses are involved and you can afford to lose only one trick is to lead a singleton, if possible, up to a king. At least if the king loses, the opponents can take only one trick and you have a second finesse available. If you take the diamond finesse first and the finesse loses, it’s over.