Used in ACOL a fter opener bids 1NT. It is used with ACOL Stayman in whicha secondary jump to 3H or 3S is invitational and not forcing.
After 2D denying a four card major, 3D is used to show at least 5-4 spades/hearts, and searches for three card major support.. Opener bids 3S witha minimum and 4S with a maximum and 3 card spade support.

With doubleton spade, opener must have at least three hearts, so opener bids 3H with minimum and 4H with a maximum.