A jump to two no-trump does not ever mean 20 to 21 points and a stopper in opponent’s suit. To show such a point count, one doubles and then bids strongly, probably to game.
A jump to two no-trump is reserved for a hand with two suits, five-five or better. Five-four sometimes works, but partner may not appreciate a four-two fit because he has two two cards in both of your long suits.
The rule of thumb is that with points, one conserves bidding room. So the unusual no-trump bid is frequently done with weak hands, less than opening. If one overcalls two no-trump and then makes a call other than pass at one’s next chance to bid, one is showing a very strong hand of 16 points or more, but that is rare.
The beauty of the bid is that one can push the opponents to the three-level with little risk. One should have a fit with partner with two five card suits.
The bidding: West with 13 points and five hearts opens one heart. After all, there does not exist a thirteen point hand I would not open. Overcalling is a different proposition. North with five-five in the minors and a weak hand jumps to two notrump. East goes to game because they have not discussed unusual versus unusual (the best defense to unusual notrump). South sees hearts making and bids five diamonds. He and North have a double fit. West passes, but this is a forcing pass. Partner must bid five hearts or double. West’s pass usually shows a minimum and no sure diamond winner. East lets the double stand because he does not think five hearts will make. One has to take any positive score they can get.
The contract: Five diamonds doubled by South
The opening lead: The jack of hearts
The lead of top of an interior sequence is usually done in no-trump only. The fourth best is the nine which is the bottom card of an interior sequence. So it is better to lead the top of the interior sequence. Here, this is fine because partner has supported them, and it is unlikely opponents would be saving (sacrificing) with the ace and queen of opponent’s suit.
The play: South wins the opening lead and leads a small diamond towards the dummy. This may pay dividends if East has the stiff ace and West pops up with the king. Declarer loses two diamonds, a spade and an ace of clubs for minus 300. Four hearts makes which would have been -620 for North and South. Five hearts goes down so East and West got the best positive score they were allowed to get. Five hearts makes if West can set up spades before losing a club.
The result: Five diamonds doubled down two for -300.
Note: West could have tried to give partner a club ruff, however this is an extremely risky line of defense since West could set up North’s clubs without getting a ruff from partner. The lead of an ace from anything other than ace and king is usually not done.