Source: ACBL
Most players learn early on that a way to make extra tricks is to “ruff losers in the dummy.” For example, if we have a trump suit consisting of A–K–Q–x–x in our hand and x–x–x in the dummy, we can create a sixth trump trick by playing a side-suit loser from our hand and ruffing with one of dummy’s trumps if dummy is void in that suit.
We still should be able to take five trump tricks in our hand, given a 3-2 division of the outstanding trumps, for a total of six tricks. But strangely, this idea of “ruffing losers in the dummy” is sometimes a bubbe maisse, a Yiddish expression for an old wives tale.
“But, wait a minute, Mel. Just how can that be? I know ruffing a loser in the dummy gives me an extra trick.” Let’s look at this more closely. What’s a dummy? I pose this question to alert us to the fact that the hand lying on the table may not be “the dummy.” The actual dummy may be the cards we’re cradling in our hand as declarer! The truth is this: the dummy is the hand with the fewer trumps. Sometimes, therefore, the dummy is hidden from view.
[box]The dummy is the hand with the fewer trumps.[/box]
Ruffing in the “long” hand, no matter where it is, is a waste of time at best and damaging at worst. We could miss the best line of play as declarer if we don’t see things for what they really are. A typical example of how we could get tricked into inferior play is when we have an everyday Jacoby transfer auction, as with these hands:
| North | South |
| 1NT | 2 |
2 |
Pass |
Suppose we get the lead of the K. When the dummy comes down our eyes may trick us into thinking we should immediately start ruffing hearts in the dummy. No! The dummy isn’t really the dummy. Our hand is the dummy. Remember, the dummy is the hand with the fewer trumps. On this deal, the real dummy is the hidden dummy in our hand. If we could mentally walk around the table and sit behind the table-dummy’s cards, we would better see that no ruffing is required in the strong hand — we have no shortness there.
If we were to win the heart lead, ruff a heart in the (false) dummy, cross to the 
A and ruff another heart in the (false) dummy, we would be down to three trumps in the long hand. It would then be impossible to collect trumps with a finesse and still be able to play two more rounds of diamonds to set up the fourth-round winner. We’d be out of trumps. The correct line of play is to win the heart lead and take the trump fi-nesse. If the finesse works, we could play the high trumps. Assuming a 3-2 division, we could then go to work on the diamonds. If the finesse didn’t work, we could play the high trumps upon regaining the lead and then, as before, attack diamonds. Let’s look at another Jacoby transfer auction:
With the same K lead, the correct line of play is to win the ace, cash the A K, play the A K and then ruff a diamond in the “hidden dummy”(our hand) before trying to draw the last trump. Our goal is not to ruff hearts in the (false) dummy. When do hidden dummies appear? Hidden dummies appear all the time, much more than most players realize. They appear any time there are more trumps on the table than we have in our hand. They appear when we use:
1. Jacoby or Texas transfers.
2. Any bid that shows two suits after which the eventual declarer chooses between the two long suits. Examples include the unusual 2NT, Michaels cuebid and DONT.
3. When a 1
opening bid has been raised by partner, responder frequently has more trumps than opener.
Be on the lookout for hidden dummies and try to be aware of the best line of play. Avoid ruffing in the long hand and risk running yourself out of trumps. Try to ruff in the short hand, no matter where it really is.