Source of tricks of notrump bid
I am attaching handout for those of you who don't already have it. The "Western Cue" can be bid when opponents open a Weak Two and you have a "Source of tricks" suit (usually a minor) and stoppers/semi-stoppers the remaining two suits. Cue bidding the Weak Two suit at the three level, e.g. 3♠ after a 2♠, asks partner to bid 3NT if s/he has a stopper in opener's suit.
This cue bid also applies in similar situations. Today, you hold ♠8 ♥AJ7 ♦K10 ♣AKJ10752. You open 1♣; LHO bids 1♠; partner passes and RHO passes. You bid 3♠. Partner bids 3NT with ♠Q109 ♥KQx ♦Jxxx ♣Qxx. You are taking at least 10 tricks.
Partner opens 1♣; RHO bids 2♥. You hold ♠1032 ♥KQ93 ♦K10975 ♣K, so you bid 2NT (invitational). Yes, you'd like another club and a spade stopper would be nice, but life is imperfect. The lead is the ♥J and RHO ducks to your ♥K. You play a diamond to the ♦A (not having second sight like Deep Finesse) and RHO shows out with a low club. After a deep breath, you play a club to your ♣K which holds. You don't want to put all your eggs in the basket of depending on LHO to have the ♠J, so you play the ♦10 to allow LHO to take the ♦J, hoping he'll be forced to do something good for you. He continues with another heart, and poor East takes ♥A and feels end-played. If East plays a low spade, you win on dummy with either ♠9 (if LHO does not play ♠J) or ♠K or ♠Q. From the carding, RHO started with six hearts to A10 and no diamonds. Also appears to have started with three spades and probably four clubs. MIGHT have discarded a low club from ♣AJxx, but ♣Axxx is more likely. So, play the ♣Q (hoping to smother ♣J in LHO's hand which was doubleton originally). All is well.
A special kind of Avoidance Play
Dummy: ♠105 ♥AK7654 ♦A1073 ♣2
Declarer: ♠AK6 ♥108 ♦KQ84 ♣K1073
Let's Pretend that matchpoint greed got you to 3NT rather than 4♥ or the almost impossible to find 6♦. Your LHO opens 1♣ and partner overcalls 1♥. RHO passes. If partner is bidding on ♥AKxxx and out in hearts (allowable at the 1 level in your partnership), you will be scrambling, but if partner has 10 points, you want to be in game, so you bid 3NT. Partner, with six hearts, but 11 HCP succumbs to matchpoint greed and leaves you there.
The lead is the ♣Q (presumably from ♣AQJx(x). Assuming diamonds behave, you have 9 top tricks, but you want more. There is no point in ducking the club because you might not get ANY club tricks if you duck this time. You and dummy have 26 HCP between you, so RHO has zero, one, or two points. Odds are very high that LHO will own the ♥Q, so it is time for an avoidance play. Take the ♣K and lead a low heart. If LHO plays a low heart, go up with dummy's ♥A. Return to your hand with a high diamond, and play another low heart, LHO will play the ♥Q. DUCK it. The best that LHO can do is cash the ♣A and the ♣J and surrender to your ♣10. You get your overtrick. (Of course, if LHO had been foolish enough to lead a LOW club at trick one, you'd be making five.)
If the ♥Q had NOT appeared on your left on the second round, you would play the ♥K and try to divine whether LHO or RHO has the remaining high heart. If you believe LHO has it, you play a third round of hearts for the same ending.