Eddie Kantar, an American great, pointed out the unplayability of standard bidding after a 1NT rebid by opener:
Opener Responder
1♣ 1♠
1NT ?
Responder may now want to sign off, invite game, or force to game with a suit bid. There are only two levels of bidding available for the three actions, however, and three into two won't go.
Our style of rebidding no trump with balanced hands means that we may miss major suit fits and we use a convention known as checkback to find them.
Over a one no trump rebid, we give up two bids (2♣ and 2♦) to this convention and it is known as two-way checkback. This allows us to differentiate easily between invitational and game-forcing hands, leaving jump rebids for hands with slam interest.
Over a two no trump rebid we only give up one bid (3♣) as the differentiation is not required and the natural bids below three no trump are too valuable.
We will mainly focus on two-way checkback as this is more frequent.
After any auction like:
Opener Responder
1X Pass 1Y Pass
1NT Pass ?
2♣ is a PUPPET to 2♦ - that is, the opener MUST bid two diamonds. Responder may pass this if they have a weak hand with long diamonds. All other bids are INVITATIONAL.
2♦ is GAME FORCING checkback. Opener makes the most natural rebid but always shows hearts BEFORE spades: that is, if responder has bid hearts, then you show 3-card heart support before showing a four-card spade suit; however, if responder has bid spades, then you show your 4-card heart suit before showing three-card spade support suit.
2♥ and 2♠ are weak.
2NT is invitational with CLUBS
3♣ is WEAK CLUBS
3♦, 3♥, and 3♠ are natural slam tries.
Opener | Responder | Auction | Comments |
♠ Kxxx | ♠ xx | 1♣ 1♥ | With a minimum hand responder shows their 4-card major looking for a fit, then settles for playing in diamonds. |
♠ Ax ♥ AQxx ♦ Jxxx ♣ Jxx | ♠ Qxxxx ♥ Kxxx ♦ A ♣ Qxx | 1♣ 1♠ | Responder shows five spades and 4+ hearts with invitational values. Opener invites and responder hopes for a good dummy. |
♠ Ax ♥ AQxx ♦ Jxxx ♣ Jxx | ♠ Qxxxx ♥ KJxx ♦ x ♣ xxx | 1♣ 1♠ | Responder shows five spades and 4+ hearts with a weak hand. Opener shows a preference. |
♠ Axxx ♥ AQx ♦ Jxx ♣ Qxx | ♠ Qxxx ♥ KJxx ♦ x ♣ AJxx | 1♣ 1♥ 3♠ 4♠ Pass | Responder shows four spades and 4+ hearts with INVITATIONAL values. Two spades is non-forcing, but Opener likes the double fit and is maximum for 1NT. Opener’s 4333 distribution means a cautious invitational raise (imagine if responder had xx xx in the minors), but many would raise directly to game. Responder accepts with good values. |
♠ Axxx ♥ AQx ♦ Jxx ♣ Qxx | ♠ KQxx ♥ KJxx ♦ x ♣ AJxx | 1♣ 1♥ 3♠ 4♠ Pass | Over the game-forcing checkback, Opener shows his 3-card heart suit before their 4-card spade suit. Responder shows four spades (and probably four hearts) and they find the best game. |
♠ Axxx ♥ AQx ♦ Jx ♣ Qxxx | ♠ KQxx ♥ KJxx ♦ Kxx ♣ Ax | 1♣ 1♥ 4♠ Pass | Over the game-forcing checkback, Opener shows his 3-card heart suit before their 4-card spade suit. Responder’s 3NT shows that they are not interested in a 5-3 heart fit, so they must have four spades otherwise they would have not used checkback. So Opener corrects. |
♠ Axx ♥ AQJx ♦ Axx ♣ QJx | ♠ QJ10xxx ♥ Kx ♦ 10 ♣ Kxxx | 1♣ 1♠ Pass | Don’t use checkback when you have an obvious bid. |
♠ Axx ♥ xxx ♦ KQxx ♣ QJx | ♠ KQJ10x ♥ AKJxx ♦ A ♣ xx | 1♣ 1♠ | Responder shows slam interest with five spades and, probably, five hearts. With 5-4 you would often use game-forcing checkback. Opener sets spades and Responder cue bids. Opener signs off, knowing that they have two club losers. |
♠ Axx ♥ xxx ♦ KQxx ♣ QJx | ♠ xx ♥ KJxx ♦ x ♣ Q10xxxx | 1♣ 1♥ | Responder shows their 4-card major before signing off in clubs. In real life you might expect the opponents to bid some spades. |
♠ Ax ♥ AQxxx ♦ Qxx ♣Jx | ♠ Qxxxx ♥ xxx ♦ xx ♣ KQx | 1♥ 1♠ | Responder shows a weak hand with three hearts. Responder would only do this with five spades and weak hearts: with four spades or stronger hearts, then an immediate heart raise will be best. |
♠ Axx ♥ xxx ♦ Qxx ♣ KQJx | ♠ KJ ♥ QJxx ♦ AJ109x ♣ Ax | 1♣ 1♦ Pass | With a game-forcing hand Responder bids their longest suit first, diamonds, and then uses game-forcing checkback to see if there is a heart fit. When there is not, Responder settles for the no trump game. |
♠ Axx ♥ KQxx ♦ Qxx ♣ Jxx | ♠ KJxxx ♥ xx ♦ A9x ♣ Axx | 1♣ 1♠ 4♠ Pass | Responder uses game-forcing checkback and opener shows four hearts (hearts before spades!). When Responder just bids three no trump, they must have been looking for spade support, so opener chooses that game. |
♠ Axx ♥ KQxx ♦ Qxx ♣ Jxx | ♠ KJxxx ♥ x ♦ A109x ♣ Axx | 1♣ 1♠ 3♠ 4♠ Pass | Responder uses game-forcing checkback and opener shows four hearts (hearts before spades!). Responder would prefer to investigate alternative contracts with a singleton heart and bids a forcing two spades. Opener raises with 3 spades and Responder places the contract. |
♠ Axx ♥ KQxx ♦ Qxx ♣ Jxx | ♠ KJxxx ♥ x ♦ AK9x ♣ AKx | 1♣ 1♠ 3♠ 4NT 5♣ 6♠ Pass | Responder uses game-forcing checkback rather than jumping because there are three potential trump suits and the space will be useful. When they find a fit, then key card is appropriate. |
Checkback is used even when the opening bid is overcalled or doubled at the one level and Opener still rebids no trump.
North East South West
1♣ 1♥ 1♠ Pass
1NT Pass 2♣=puppet to 2♦, either to play or to show invitational hands
2♦=game-forcing checkback
2♥=asking for heart stop
2♠=natural and non-forcing
All further bids by either partner retain the usual meanings, except that a natural bid in an opposing suit can show either four cards or a strong three. For instance, after the heart overcall, a 2♥ response by North would show four hearts with at least one honor or three good hearts (while denying three-card spade support).
Checkback does not apply if the fourth hand bids (or doubles) or if the one no trump rebid is doubled. The bidding reverts to standard bidding in these cases.