North has 20 points but does not have the shape for 2NT. In fact, he likely has more points in a suit contract.
He opens one heart showing five hearts (we play five-card major openings) and South knows they have the golden fit in hearts of at least eight cards.
So he bids one spade with the intention of showing heart fit if partner does not have four spades as well.
North knows they have at least 26 high cards points and a four-four spade fit. He, therefore, jumps to four spades, which is game in the major.
More points can be scored if they bid and make game than if they play in a partscore (any contract below game).
West has no obvious good lead. He does have obvious bad leads. Leading the top of an interior sequence, the queen of clubs, is not done on the opening lead. He cannot lead hearts because North has declared length and strength in that suit. One hardly wants to help declarer by leading his side suit.
A diamond lead is bad because, from the bidding, partner is likely to have four points or less.
The opponents probably have 25 points for their game bid. Unless partner has the queen of diamonds, a diamond lead just finesses West. Chances are not good enough to lead a diamond.
The only suit left is trump. West leads his second trump. Leading high low is normal with a doubleton when you want to tell partner you can get a ruff.
However, that is not the case when leading trump. So why give declarer any more information than the lead does already?
South wins the opening lead and plays a club from dummy to his king.
One leads up to lone kings and it has a 50 per cent chance of winning if East has the ace. It loses and back comes another trump.
South leaves the last trump out.
He cashes the ace of diamonds and then all of his hearts, pitching (throwing away losers) two diamonds from his hand.
South will not draw the last trump and will not let East do it on his own. He wants two diamond ruffs (trumping a loser) and two club ruffs.
If East gets in, which he can’t do unless he ruffs, he would want to play his last trump so declarer gets one more trump trick but two less ruffing tricks.
The defenders will get the ace of clubs and a small spade whenever East takes it.
South will make five spades for +450, and if he draws three rounds of trump, he will make four spades for +420.
-The four-four major fit is better than the five-three major fit because he can ruff with either hand in spades and he can pitch losers on the long hearts which he cannot do if hearts were trump. Four hearts can only ever make four for +420.
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