Only use when partner opens 1NT.
Bidding 2 clubs asks whether opener has a 4 card major.
If opener has 4 card major then she bids that major at 2 level.
If she has 4 spades and 4 hearts then bids 2 hearts.
If she has no 4 card major then she bids 2 diamonds.
Responder must have a plan for whichever answer is given and bid accordingly after openers reply.
Opener must not bid again.
If opposition overcalls or doubles the opening bid then the stayman convention is off and all bids are natural.