Forcing No Trump is the work horse of the Two-Over-One bidding system. One No Trump is a forcing response (one round) to an opening in either major. It tells partner, that he cannot bid a new suit at the two-level because he does not have an opening hand. He could have anywhere between five and twelve HCP’s. The bid cannot be passed unless made by a passed hand.
The opener must then bid his second longest suit. He could be bidding a three-card Diamond suit or a two-card Club suit if he has four Spades and is not strong (16 HCP’s) enough to reverse into Two Spades.
With 5 to 9 HCP’s, the person using Forcing No Trump will be happy with the two-level and will likely run to his partner’s major with two of them.
With 10-12, the person using Forcing No Trump, will either raise partner to the three-level or rebid Two No Trump.
The bidding: North, with 13 HCP’s, opens One Heart. Partner does not have an opening hand or four Spades and replies with a forcing One No Trump. North bids Two Diamonds and South bids Three Clubs showing a suit of his own.
Three Clubs shows a reasonable six-card suit, but if South were not in the upper range of his bid, he would have to pick one of partner’s suits. North has a fit for Clubs and has the 14 HCP’s to accept the invite to 3NT, but with a singleton Spade, he refuses to bid Three No Trump because the opponents have at least nine Spades. Partner denied four Spades in bypassing them to bid forcing One No Trump.
The Play: West leads his 4th best Spade. Declarer wins the ace and then ruffs a Spade. He goes to the Diamond Queen and ruffs another Spade. He then leads a trump towards the King. West wins the Ace and exits a Spade. Declarer ruffs, plays a Club and claims the rest for +170.
Note: Two Diamonds will not fare nearly as well. The opponents will likely lead trump every chance they get and declarer will try a cross-ruff. He can find eight tricks for +90.