Two-Over-One is a better bidding system than Standard American because bidding becomes simpler once the game force is on. Furthermore, slam exploration can easily take place below game.
The bidding: North, with his 17 HCP’s, opens One Spade with the intent of rebidding Hearts. South responds Two Hearts showing five Hearts and enough values for game opposite a minimum opener. Now North can bid Three Hearts showing support and leaving room for slam exploration. North would use the Principle of Fast Arrival and bid Four Hearts with a minimum.
In Standard American, North could not bid Three Hearts as that would be invitational. He would have to bid Four Hearts and partner may be reluctant to make a slam try above game. He could make a temporizing bid, but partner would not know if a delay was made because of slam interest or a poor fit.
This is a huge benefit of Two-Over-One. South knows they have a Heart fit and partner has extra values. When one goes to game slowly, once a fit has been found and a game force has been made, one is making a slam try.
South shows first round Diamond control and North shows the Spade Ace. South bids Four No Trump asking for keycards. North has two with the Heart Queen. South asks for Kings which shows the possession of all the keycards. He cannot bid seven even though they have all the Aces and Kings because he needs to know about the third round of clubs.
The Play: West leads the Diamond Seven because his holding in the other unbid suit is four to the Jack. One tries not to lead from Jxxx or Qxx. Declarer wins the King and draws trump. He discards a club on the top Spade and ruffs two Clubs and claims. When East shows out in Clubs, there is a ruffing finesse available but not needed.
