During the Covid period where everyone was playing online, I received numerous cases to review. Accusations of "self-kbbitzing" or being on the phone with your partner were rampant. One player was recorded for this action: Holding 

 A2  
 A6  
 653  
 AJ9632,
 he opened 1. Partner responded 1 and he rebid 2. Partner now bid 2.  What would you do? I think 3 or 3 are the main possibilities. This player jumped to 3NT. He caught partner with a suitable dummy with diamonds stopped. 3NT is a terrible bid, but you can't convict a player based on only one such action. Maybe he was just a bad player, or made a bad bid. Anyway, this was the Real Deal:

	A2  A6  653  AJ9632
1083  J97  A10874  85		Q964  Q432  Q9  Q107
	KJ75  K1085  KJ2  K4

The teacher in my saw an opportunity. The start of 1-1-2 is fine. But South's 2 makes no sense. There is no 4-4 spade fit (North would have rebid 1 with 4), so South has a 100% 3NT call at his second turn.

West would lead the 7 (4th best) and East would play the Q.

Now what? If South takes the K and works on clubs, East gets in and plays another diamond, down one.

This is a safe-hand/danger-hand lesson. Declarer has to realize that East is the danger hand. If he gets in and plays another diamond (and they are 5-2), he is down. So, he should holdup on the first diamonds. If they turn out to be 4-3, no problem.

Once East wins the first trick, there is no defense. Declarer will eventually work on clubs and easily make his contract.

What about winning the first trick and playing A, K and another club? That will work if East started with any doubleton club (or singleton 10), but why rely on this when the indicated line works on most normal layouts.