By Kenneth Konstam and L. Tarlo (Konstam And Tarlo).

(*) Named this way after the initials of his creators.

Cue-bid K.A.T. convention is used in order to enter into the bidding over an opening bid at 1 level made by an opponent, giving same time to partner indications enough accurately about the force and the shape of the hand. Proceeding from this convention, a direct cue-bid in the opponent's suit can be made with a weaker hand than usual and it is forcing only for one round, except the case when in the next round of bidding the cue-bid is repeated, showing this way enough force for making a game with minimum help from partner.

Example: 1)
E        S        W        N
1H     2H (a) pass   2S (b)
pass  3H (c) etc.

Explanations: a) forcing for one round; b) partner is obliged to show his best suit; c) game-force, partner is obliged to keep the bidding open until a game is reached or a penalty double is made against the opponents.
Relying on this principle, the overcalls within the framework of K.A.T. convention are made this way:

10-12 hcp - Take-out double with a good support in the unbid major(s).

Example: 2)

S- A J 9 5                     E        S        W        N
H- K Q J 10 3              1D     dbl      pass     2C
D- 8 4                         pass   2H      etc.
C- 7 5

13-17 hcp - Cue-bid K.A.T. with a good own suit and good support for the unbid major(s).
Forcing only for one round.

Example:  3)

S- Q J 9 5                    E        S        W        N
H- 7 3                          1H      2H      pass   2S
D- A K J 8 3                pass    3S      etc.
C- K 7

15-17 hcp - 1NT, balanced shape, two stoppers in the suit of the opponents and probably short in one major.

Example: 4)

S- A Q 7                       E        S        W        N
H- 9 4 2                        1S      1NT   etc.
D- A Q J 4
C- Q J 5

18+ hcp - Cue-bid K.A.T. followed in the second round of bidding by a repeated cue-bid with an unbalanced hand or 2NT with a balanced hand.
These two rebids - first being game-force and second being strong invitational - has to
be made only with hands that assures making the final contract even when it happens
that partner has a very weak hand.

Example: 5)

S- A K 5                      E        S        W        N
H- A K Q 9 7              1D      2D     pass     2S
D- 4 2 pass                3D (a) etc.
C- K Q 3

Example: 6)

S- A Q 7 4                   E        S        W        N
H- K 10 6                    1D      2D     pass     2H
D- A Q J pass            2NT (b) etc.
C- Q J 9

Explanations: a) repeated cue-bid, game-force; partner will bid further on, repeating the spade suit if it is a 5-card suit or a second 4-card suit; b) game-invitation; with any useful values partner will bid the most attractive game contract.

It is to be noticed that for overcalling with a cue-bid K.A.T. over an 1S opening bid of an opponent, the hand should be a little stronger because there is the danger of the bidding growing up fast to a higher level. Conversely, over an 1C opening (normal opening, not strong) the cue-bid K.A.T. can be a little lighter because there are good chances the bidding will stop at a lower level.

Within the framework of this convention, the suit overcalls at level 1 show a weak hand with an acceptable suit, while the jump overcalls show a strong 1-suiter hand, too strong for a take-out double.
K.A.T. convention is highly appreciated in Great Britain. It can be used with success so much in the 2nd seat or in the 4th seat.