To Cover or Not to Cover

Whether to cover an honor or not is, in my opinion, about the most neglected of frequently recurrent situations. And from that, one of the commonest of defensive errors. No, you don't want to cover an honor with an honor because you read it in a book or a mentor told you so. You want to cover an honor with an honor to promote values for your side. And you don't want to cover when it is apparent that you can't do your side any good by covering. Sound simple? Well, of course it's not. That is, it's not always simple, for there are going to be ambiguities where you'll just have to do your best. But then there are times when the situation is fairly simple if a defender keeps his wits.
In a recent tournment, I came across two improper covers and thought I'd give them both here.

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

Opening lead against three no was the 3 of spades, which declarer properly let ride to his king, as East, also properly, went third hand high. Declarer wants to let it ride, because he wants to preserve an entry to dummy, and he's got enough stuff in diamonds to unblock the spades when he must. At trick two, declarer cashed the king of hearts, played the jack, covered, and up went declarer with the ace. The jack was covered!
No, West definitely must not cover here. Yes, he still has the 8 to win the fourth round of the suit, but that's all. Please note that declarer cannot pick up West's queen on a non-cover and that there's a difference between holding the Q for fourth round control and the 8. The difference is that on a cover, declarer is now in dummy and can establish the heart suit, conceding a trick to the 8. But on a non-cover, declarer can only let the J ride, use up his sole entry to cash the A of hearts and then abandon the suit.
Declarer will have five heart winners on the cover. He covers the queen, cashes the 9 . . . well, he might think of not cashing the 9 just yet. He has to lose a heart to run that holding, and it doesn't matter whether it's the 3rd or 4th round when it comes to heart winners. Where it does matter lies in what he sluffs. He can't afford to sluff any clubs and doesn't want to sluff two diamonds. So at trick four, he leads a low heart, sluffing a diamond.
Declarer now only has to sweat out some danger in clubs, though we can see the defense can't take more than two clubs and declarer should have been on his way to an overtrick.
You might note that had declarer another entry -- let's say we exchange the king of diamonds with the 8 -- it wouldn't matter. Declarer can ensure 5 heart winners by pushing the jack through if uncovered. Or if covered, he wins and can ensure 5 heart winners by conceding one to the 8. So it's really the lack of entries that makes the cover ill-advised here, which I cite in part to say, you don't know what factors will surface to make a cover advisable or not, and it's up to the careful defender to be ready ahead of time, especially at the real table, where fumbling around becomes a dead giveaway, and to work out the possible gains against possible losses on a cover.
It shouldn't have been. But, oh, by the way, it didn't cost the defense anything! Declarer didn't seem to notice that he'd been given a gift. He now took a losing diamond hook and a spade continuation by West killed the run of hearts. To be sure, declarer could still have made his contract by cashing the 9 of hearts and picking up 3 tricks in every suit but clubs, which makes 9. But he didn't seem to notice the value of that 9 and so went down.
However, I hope the fact that it didn't cost anything doesn't induce West to overlook a lesson here and note how close he came to allowing declarer more tricks than he deserves. Next time it might be costly. Very costly.

A 6 3
A Q 10 7 5
J 10 8
10 2
K 5 4 J 10 9 8 2
8 6 4 3 2 K J 9
6 5 3 7 2
K Q J 5 3
Q 7
------
A K Q 9 4 Vul: N-S
A 9 8 7 6 4 Contract: 6 clubs

WestNorthEastSouth
1
Pass 1 Pass 2
Pass 2 Pass 3
Pass 4 Pass 5
Pass 6 Allpass

Six clubs. Bid and made. How on earth does one make 6 clubs when there are two trump to lose, I wondered. And you already know the answer. Declarer took the opening heart lead in dummy, sluffing a spade, led the 10 of clubs, covered by East, won by declarer -- and the queen falls on his left! Well, hello there!
This case isn't quite the open-and-shut case that the first hand displays. There the defender could have and should have seen the whole suit by the play of that jack of hearts. Dummy was showing 6 pieces, the defender held four, his partner followed to the first round of the suit, and now declarer was laying down the only heart West hadn't seen yet.
Here, however, well, you'll need some common sense along with drawing some inferences from an opponent's bidding, which is to be sure, not an exact science, plus a recognition of why you cover. First: when you cover, you do so to promote a lower card. The higher cards can take care of themselves. So if you cover a 10, you do so to promote a nine (or maybe an 8), but not to promote a queen or king.
Could East's partner hold a 9 that can be promoted? Well, we can't call it impossible. He could hold A 9 low, fr'instance. The cover would then make East a hero. The K 9 low would also do it. Is it then not a tossup? No, I wouldn't say so. Not at all. First, West would have to hold either of those specific tripletons. And the more specific you need your partner's holding the be, the less likely you'll find it. The Q 9 x wouldn't help. You've got one and only one trick coming whatever you do. The 9 with 3 kickers would give declarer a 4-card suit which is improbable in view of the bidding. And any six-card holding by declarer would render the cover either pointless or counter-productive.
Now, though people do sometimes make bids out of whack with their hand by "normal" standards (and here they are in the wrong contract, as will be discussed below), you still had better attribute adherence to usual bidding practices to your opponents. You'll be right far more often than wrong. Here declarer opened a club, reversed and then went back to clubs all before his partner offered any support. It may not be certain that he holds 6 clubs, but you've got to suspect it, and further, if it's only a 5-card suit (and with 5-4 in the minors, don't you think he might be inclined to no trump opposite his partner's bidding?) you've got to suspect that your partner isn't likely to hold just the tickets for making the cover productive.
In any event, it was a very, very expensive cover. Six diamonds was being made by any number of pairs. These people were in the wrong contract, and the ill-advised cover handed this pair a parity with those whose opponents were in the right contract. Lemme see what it cost. 13.22 IMPs to the declarer. Beating the contract would have brought 6.28 to the defense. Oooooh, that's very expensive. Unlike the first instance, the non-cover isn't guaranteed to be right. But a little thought should make it at least as attractive as the cover. Yes, you want to cover honors, to "sacrifice" your cards for the good of the partnership, which some find a little difficult to do. But you don't want to do it without reflection.

I have discussed covering honors here and reasons for not covering here. The bidding was faulty on two counts: let us start with preference. I have called it the easiest bid to get right, particularly when you're preferring between the two majors or the two minors (as here). You pick the suit where you have the greater length. And if you have equal length, you pick the first suit bid.
You might notice that the reason people can make 6 diamonds but not six clubs is that they can lose a club and ruff out the third round before drawing trump and thus make their contract. This was one of the reasons offered here for why balanced suits for trump tend to work better than an unbalanced -- it's not an absolute certainty -- when you have a choice. Five people made six diamonds. Two declarers were in 6 clubs, one didn't make it; the other was the above declarer.