South had 11 sure tricks and needed a 12th from one of the major suits.
One possibility is to use it to show major suits.
If he returns a major suit North will win, cash the heart jack and play the club king.
West had to guess which major suit to lead, and guessed right by leading a heart.
North is almost certain to have four cards in one or both major suits.
But he was concerned about other possible breaks in the major suits.
West's raise suggested that he was happy to play in either major suit.
The major suits were now stripped, but the lead was in the wrong hand.
And both major suits were due to break badly for South.
By this means all 5-3 and 4-4 major suit fits can be found.
