BRIDGE NOTES: The Check Back convention and its application

Question: What is the range of 'Check Back' convention. Can it be applied playing strong No Trump? From. Zafarul Haq. Karachi.
Answer: It is very appropriately said that bridge is the game of communication between the partners by bidding to arrive at a suitable contract and by signalling while playing the cards. And hundreds of conventions have been invented for the benefit of partners to precisely convey the shape and strength of the hand to one another and make moves with the help of discarding signals. The Check Back convention is one among them which is applied by the responder by bidding artificial two clubs in his second round having bid one of the major suits earlier at one level to communicate a particular type of hand to the partner who has opened the bidding with one of a minor suit and rebid one No Trump. This convention is known as 'Check Back Stayman' convention and also 'Delayed Stayman' and 'Secondary Stayman' convention, which is applied in the second round of bidding. There are other variations of this convention like 'Crowhurst' and 'New Minor forcing' bids.
There is a limited scope of application of this convention in strong One No Trump opening bid. But only in case forcing two clubs response to one NT has been agreed between the partners. Those who play two-way Stayman may not find room to apply this convention on forcing two diamond response and weak two club response does not fit in the scheme of this convention. As the prerequisite of 'Check Back' convention is a positive game going hand with one five card and another four card suit with the responder. Otherwise there are a variety of natural bids available for appropriate responses to make a game the strength of hand permitting.
The range of application of Check Back convention is given as under. In all cases it is forcing to game or a slam if the opener or responder has the requisite strength or distributional value. Primarily the idea of the convention is to find a 5-3 or 4-4 fit in major suits.
Playing weak NT 12-14 and opening the bid with one club and rebidding with One NT on one spade response shows 15-17 range with balance hand for example:

(1) 1C          !S
   1NT         2C
   2S

In this sequence the 2C bid by responder is Check Back for locating fit in major suits.
By bidding 2S the opener shows 3 cards of spades and no more than 3 cards of hearts.
The responder's hand would be something like:

(2) S KJ1097 H AJ98 DA96 C5
(3) 1C            !H
   !NT            2C

In vulnerable position the opening bid can be better minor with 13-14 points. The responder seeks 3 card support for hearts or 4 card spade with the opener by applying 2C
Check Back.
With no three card heart and only three card spades the opener bids 2D as denial bid; nothing to do with diamonds.

(4)  !C                 1H
      !NT               2C
      2S            

The bid of 2S by the opener shows 4 card spade suit and no more than 2 cards of hearts.

(5)  1C                 1H
     1NT                2C
     3C

The opener shows 4 spades and 3 card hearts.

(6)  1D                   1S
       2NT                3C

In this jump bid the opener indicates 18-20 pointer hand and 3 C by responder is check back with the intentions of safe slam contract if suits fitting is found or in NT otherwise.
The bidding sequence would proceed in the following pattern if the responder's hand were weak.

(7)  1C              1S
    1NT              2D

Since the responder did not apply check back, his hand is weak and he wants preference from the opener for one of his suits or he may choose any other bid to sign off below game.
Please note all the conventional bids are alertable.
Golden tips
The conventional bids are devised to meet specific requirement of hands. Therefore they should be strictly followed with understanding between partners to avoid faux pas in their application.