The WGM Gabriel Chagas, once explained the way to play this kind of weak suits, he called the technique the Intra-Finesse.
Dealer West All Vul.
West
North
East
South
Pass
1
Double
Pass
1
Pass
3
Pass
4
Pass
Pass
Pass
When East cards lay down:
Q 6 5 3
K 9 4 3
J 8
9 8 7
A 9 8 4
A Q 6 5
A Q 4
4 2
Contract: 4
Lead: J
After the lead, and before touching a card declarer made his plan, he had two club losers and the contract depended not only on the diamond finesse, but also in losing only one spade trick.
West covered the lead with the Q, played the A, both defenders followed the suit, he played a third heart round playing the K from his hand and continued with a diamond to dummy’s Q…winning the trick, first success!.
The declarer reviewed the hand, four trump tricks from dummy, and three diamonds, now it was time to attack the spades suit. The problem was that North surely had the K, so playing a little spade to the ace and a spade to the queen could not work.
The WGM Gabriel Chagas, once explained the way to play this kind of weak suits, he called the technique: the intra-finesse , and West used it in this hand.
After winning the trick with the Q, West played dummy’s 8, South played a little spade and declarer also played a little one from his hand.
North won the trick with the J and returned a diamond, West won with his J and played the Q. That was enough, North played the K, while everybody in the table saw South playing his 10, 10 tricks… the end = finito.
The whole hand was: