Used by responder with at least invitational values to discover whether partner's 1/2NT bid may consist of a 5 card major suit.

1N/2N - 3♣:

• 3♦ - at least one 4M;

  • • 3♥ - 4♠;

    • 3♠ - 4♥;

    • 4♣ - both majors, slam try, total ~28+ HCP;

    • 4♦ - both majors, weak,

• 3♥ - 5♥;

• 3♠ - 5♠;

• 3N - no 4M, no 5M.

1N/2N - (P) - 3♣ (X):

• XX - 5♣, no major;

• 3♦ - 5♦, no major;

• P - at least one 4M;

  • • 3♥ - 4♠;

    • 3♠ - 4♥;

    • 4♣ - both majors, slam try, total ~28+ HCP;

    • 4♦ - both majors, weak,

• 3♥ - 5♥;

• 3♠ - 5♠;

• 3N - no 4M, no 5.