A redouble in direct seat shows 10 or more points implying no fit. Last week, we saw how a new suit at the two-level is just a good suit and is less than ten points. The redouble allows one to have less than ten points.
The bidding: South with 14 points and no five-card major opens his longer minor. West doubles one diamond with four-four in the majors and 15 points. If West had 4-3 in the majors or double diamond stoppers, a one-notrump overcall would have been the correct bid.
North has a good club suit, but he has ten or more points and should redouble. This tells partner that any subsequent double is for penalty, implying no fit.
North cannot double one spade and bids two clubs. This is all South needs for three notrump.
The contract: Three notrump by South
The opening lead: The jack of spades
The jack is top of a three-card broken sequence, jack-ten-eight. Partner has zero points from the bidding and from what West can see in his own hand. Therefore, a heart lead would be bad. A spade lead and a spade continuation every time West gets in is the best.
The play: Declarer wins the spade and drives out the club ace. West realizes he may not get a heart trick and leads the king. South runs clubs and then knocks out the diamond ace. West cashes the heart queen keeping declarer to only one overtrick. Without the heart switch, declarer makes two overtricks. Declarer wins five clubs, three spades, one diamond and one heart.
The result: Three notrump by South making four for +630