Double Barreled Stayman
Over 1NT, 2C and 2D ask opener for a four card major. 2C is not forcing to game. 2D is game-forcing.
Over 2D, opener re-bids:
2H or 2S to show four
2NT with 4-4 in the minors
3C, 3D, 3H, and 3S to show 5 of that suit
3NT with exactly 4-3-3-3 with 4 in a minor