A Three-Way Lesson

K 5 2
A Q J 10 2
A 8 2
J 8
A 10 9 8 4 ------
9 K 7 6 4 3
10 6 5 Q J 9 4 3
10 6 5 4 Q 7 3
Q J 7 6 3
8 5
K 7 Contract: 3 NT
A K 9 2 Opening lead: 10 of diamonds

This hand could have been put in Count Your Winners or So Who Wants to Finesse? or Entries, so I thought I might as well put it in this catch-all category. And Hold-up also, which I didn't recognize till I ran through the 3rd declarer's line of play! Three declarers went down here, all getting an opportunity on the identical play and identical discard by an opponent. Two made the play at trick 2, one at trick 3 after holding up one round on the diamonds. The play was a spade to the king, East discarding the 3 of hearts.
Now that discard should have told declarer 2 things, one of them certain, the other probable. The certainty is that spades aren't going to be your path to a winning contract here (you've only got one more spade winner coming); the probability is that with only 5 hearts left, the defense won't be able to protect the 5th round of the suit. If that is so . . . well, how about laying down the ace of hearts. If everybody follows, the defense now has 3 hearts left, and they must be exhausted on the play of the Q J 10, making the 2 good for a trick. Count 'em up and that's 9 with no possibility of their running 5 tricks..
You don't want to finesse here. It's not necessary for nine tricks and it's not likely that you'll pick up the king anyway. There's a 50% chance that it's offsides and an X% chance that even if onsides, it'll be guarded too often to be picked up, while you exhaust the closed hand of stoppers as you shift the lead to take the finesse -- twice? So lay down the ace of hearts, and the rest should be easy. One declarer, indeed, (with a diamond opening lead) did maneuver a finesse by entering the closed hand with a club and the 10 held! Now, what do you do? Wipe out your remaining club stopper to take a finesse again that still won't necessarily pick up the king, which indeed is offsides anyway, as your RHO had just made a shrewd play?
So declarer would do well to lay down the heart ace very quickly. The king of spades holding the trick was a lucky break. Had this been taken by East and a diamond shot back, your entry to exploit your hearts would have been eliminated. All were given this opportunity. Here is what they did after the king of spades held:
One came to the jack of spades, which was sure enough going to establish an entry -- eventually, and too late. West won and (naturally) shot a diamond to the ace, and now declarer doesn't have an outside entry to exploit the heart suit. Another spade lead to the queen allowed declarer to take the heart finesse, but it didn't work, and East was able to cash two more diamond winners (declarer had held up the first round) for down one.
The declarer referred to above as finessing the 10 of hearts, holding, illustrated what I said about the finesse costing too much in chewing up the closed hand's stoppers. Declarer now tried to manufacture another entry with a spade to the jack, same as the one above, and he rightly got the same reaction from West: A diamond through the ace (in this case), as declarer ducked. But East was able to continue the suit, and once again, the heart suit, the most potent of declarer's four suits, was reduced to one winner! When he repeated the heart finesse, he got what I suspect was a bit of a surprise.
You don't want that finesse when you can make a tricky contract without it. You don't want to risk having that lone entry, the ace of diamonds, wiped out before you're ready to run hearts. You can't afford it.
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[Years later: this hand got more interesting with age. In going over this third declarer's line to be sure I'd been right about a hold-up in diamonds, I found some interesting tidbits I hadn't noticed before.]
A third declarer got a club lead. Declarer played the J, covered by the Q and won in the closed hand. When a lead to the king of spades held, declarer came to the K of diamonds with impunity, finessed the 10 and East, unlike a confrere referred to above, took the trick! Now how did declarer go down from there? The hand then looked like this:

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

East now led a club and declarer ducked! Declarer had 9 tricks at his fingertips (2 clubs, 2 diamonds, four hearts and a spade), but now has no access to his K of clubs! -- except through knocking out the A of spades. But West was just given the opportunity to knock out declarer's last diamond stopper. Had diamonds been originally 4-4, declarer now couldn't make the hand as the defense cashed two diamonds, a spade, club and heart.
West took that trick with the 10 of clubs and led a diamond and the hand looked like this before the diamond lead:

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

Declarer must duck the diamond lead, since he has to knock out the A of spades, and hope like the dickens that West started the hand with only three diamonds, which was indeed the case. The hand would then look like this:

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

That's only the third winner for the defense and we can see that declarer is perfectly safe (though he doesn't know it yet). Declarer now has a choice of winners, since the 9 of clubs can be one itself. Declarer must cash three heart winners, sluffing two spades. He can cash a fourth, sluffing the 9 of clubs if he wishes. But having jeopardized his contract needlessly, he at the same time established the 9 of clubs and doesn't need to know he had 4 heart winners. And now lead a spade to the Q J.
Unfortunately, having jeopardized his contract by ducking a club lead, declarer now ensured his defeat by not ducking that diamond lead from West (i.e., on the second last layout above, not the one immediately above, which declarer didn't reach). Now it doesn't even matter whether he noticed that gift in hearts and recognizes a fourth heart winner. He has no access to his 9th winner in the form of the K of clubs. West won the spade lead and hit his partner with a diamond and East ran three to set the contract. This declarer, with two ways of making the contract, by either not holding up in clubs and cashing out, or holding up in diamonds and getting that last piece of luck (that West started with only 3 diamonds), was down two, losing three diamonds and one in each of the other suits.)

Oh, the lessons offered: The hold-up both ways! when not to (i.e., you can cash out and may not be able to if you duck) and when to do so. [For defenders] Keep the same number of cards in a suit as dummy shows (insofar as practical). I would think any defender with 5 hearts back of 5 in dummy would recognize that he'd be giving up a long heart. I have instituted that category -- keep the same number as dummy shows -- with illustrations since this was first entered. Watch discards and count. Well, rather obvious. But valid.
Lastly, East gave declarer a second gift in taking the first round heart finesse. I have no category for that, no maxim. Still, if East is pretty sure declarer is going to need that suit, he might reflect on the damage he can do by ducking the first round. Declarer couldn't duck the second round of diamonds then, since that would then be his last entry to dummy!