Source: Think in Reverse
This deal is from the 2009 Team Trials played in White Plains. You deal as South with both sides vulnerable, holding: 
5 
K Q J 9 5 
A 9 8 
K Q 9 2
You open 1 and partner responds 1. Your rebid is easy; 2.
Partner now bids 2, fourth-suit forcing to game. You can bid 2NT because you have diamonds stopped, but I prefer 3, which gives partner a nice picture of your hand. He will know you have five-plus hearts, four-plus clubs, at least three diamonds, and therefore short spades.
This information helped us to reach 6 (the rest of the auction involved RKC). The opening lead is the A and you see:
Vul: Both Dir: South
| 9 8 7 6 A 10 2 K Q 2 A 4 3 |
| 5 K Q J 9 5 A 9 8 K Q 9 2 |
The fact that you were short in spades was good news to partner–he knew that all of his cards were working.
After the A the defense continues spades and you ruff. What is your plan?
The only possible loser in your hand is the fourth round of clubs. If clubs split 3-3 you will have 12 easy tricks (unless hearts are 5-0, but that wouldn’t be fair). What if clubs are 4-2? You still might survive in one of two ways: 1) West has doubleton jack or doubleton ten (or doubleton jack-ten). Then you can cash two top clubs and guess to finesse your 9. 2) Maybe one defender has only two hearts and two clubs; then you can draw only two rounds of trumps and ruff the fourth club in dummy.
I am just playing with you. This is one of those hands where you have to consider a dummy reversal.
What if you can ruff three spades in your hand? Now we’re talking. As long as there are no bad splits (especially 4-1 trumps), you will have 12 tricks regardless of how clubs behave. Furthermore, if you time it right, you can combine all your chances.
After ruffing the spade, you lay down your K (all following) and then continue with a second heart to dummy. Why draw two rounds of trump if you are planning on reversing the dummy? Because if trumps are 4-1, you can’t ruff even one more spade in your hand–you will let the opponent with four trumps end up with more trumps than you. If you find out hearts are 4-1, you will abandon the dummy reversal plan. But, when everyone follows on the second heart you are in business.
In dummy, you can ruff another spade in your hand. Then you cross to the A and ruff dummy’s last small spade with your last trump. All that is left is to travel to dummy in diamonds and draw their last trump. On that last trump, you throw away a small club and claim.
This is a textbook example of a dummy reversal with the added twist that you can change plans in midstream if the trumps don’t split. (In real life, I hate to say, trumps were 4-1 and clubs were 6-0–the wrong way–so I had no chance to make my slam.) However, if I were dealing the cards, this would have been the Real Deal:
| 9 8 7 6 A 10 2 K Q 2 A 4 3 |
||
| A J 10 4 8 7 J 10 3 J 7 6 5 |
K Q 3 2 6 4 3 7 6 5 4 10 8 |
|
| 5 K Q J 9 5 A 9 8 K Q 9 2 |
With this fairly normal layout, all plans fail other than the dummy reversal. –
See more at: https://www.larryco.com/bridge-learning-center/detail/203#sthash.5v1QgNf1.dpuf