We have reached the last step of bidding major two-suiters opposite a one-no-trump opening: a strong hand with at least two five-card suits. You may have your own method, but mine is to respond three spades — as in today’s deal.

Over three spades, opener may bid game in either major. However, if he has a suitable hand for a slam, he rebids four clubs to say that he likes hearts, or four diamonds to establish spades as trumps. Here, North’s hand is borderline between four spades and four diamonds.