Second Hand Low II

3. Sometimes you'll want to go low to give your partner a chance to cash a high honor (or two). This is a fairly common situation (a real-life example is given in example 2):

J 9 6 3
Q 4 A 8 2
K 10 7 5

Declarer leads off the board, East going low. Now declarer might guess "right" the first round, going up with his king. But if East goes low one more time on a lead from dummy, his partner will get his queen, and East later his ace (if the suit goes to the third round, as it must if trump). There won't be anything declarer can do about it.
You might note that the above holding is this layout which you've seen 100 times as declarer:

Q 4
A 8 2

If you want to make a winner out of the queen, you lead low from the ace. If West goes up with the king, you can later cash the Q, and with an entry to the closed hand, cash your ace. The exact same way to get two tricks when you're defender and when you're declarer.
[This situation was added to the previous page for "Why" on a look two years later, and I was surprised to find it here. However, I believe I'll let it stand, especially since here I had turned the situation 90 degrees and showed how it's identical to ace low, low opposite queen low as declarer.]
The same principle holds in this self-evident situation:

Q 9 5 4
A 7 K
J 10 8 6 3 2

Declarer leads low from the closed hand in this trump suit. Now you know you're not going to be skunked out of your ace and so should go low to allow for the possibility that your partner has a stiff king. And note this situation:

Q 9 5 4
K 7 A
J 10 8 6 3 2

Declarer leads low toward the queen. Could he, would he . . . no, he wouldn't underlead an ace in the hope of getting me to duck with a king doubleton, would he? It's not bloody likely. If he's got the ace, why doesn't he finesse if he's got the jack, or bang down the ace in the hope of catching a stiff king. But don't quote me as saying it absolutely cannot happen!

K 9 5 4
A 10 7 6 2 Q
J 8 3

On this layout, though West can't assure his partner of a chance to cash his honor, he does give East a chance to make use of that queen. The queen is going to force out the king (or win the trick), ensuring the defense with two tricks in three leads of the suit. If West goes up, he completely nullifies the value of the queen and not only allows the opponents two tricks in the first three leads, but a marked finesse against the 10 with the K 9!

Sometimes you'll want to go low to kill an entry at the proper time:

K J 10 7
A Q 8 5 6 3 2
6 4

Declarer has no outside entries to dummy, and declarer leads low. If that's a doubleton, you'll want to let declarer have that trick and go up on the second lead, thereby cutting declarer off from those goodies, for one trick in the suit. How do we know declarer has a doubleton? Of course you don't know it and there is no intent to say here that you do. But on a fairly balanced hand, you, well, take a position. The cards could be that way. You're not always going to be right, but you're going to cost your side more tricks in the long run if you always hop up with that ace on the ground that you're never getting more than one trick in the suit anyway.

A 7
8 7 5
K Q 9 8 6 3
9 8 2
J 10
K 8 6 3
A 7 2
Q 10 7 3

Playing against three no, West got off to the best possible lead of the jack of spades. Declarer ducked, East won with his king, and knocked out the ace of spades. Declarer came to his hand with the ace of clubs and led a low diamond. Now West nullified his killing opening lead by going up, and declarer, with one more diamond and no spade lead from West, was able to recapture the lead and run the suit.
West should surely duck one round. The real crunch will come if declarer re-enters the closed hand and leads the suit again. Do you duck one more time, giving declarer two tricks in the suit, or go up, giving him one -- unless he started with 3 diamonds. Obviously there's no "correct" answer that could cover all such situations. I can only say again you have to form some sort of picture of declarer's hand. Don't grab too early. The times you gain by grabbing early will be far offset by the tricks you save if you play declarer for a fairly balanced hand and take the second lead of the suit here.