A bid, on the second round, of a double jump shift or more, shows 4 card support for partner's suit and two or three cards in the suit bid. It implies shortness in one of the unbid suits. .BR>
South North
1C 1H

3S shows four card heart support plus two or three spades (usually three), and implies a singleton or void in diamonds.
South North
1S 4C!

4C shows four card spades support and two or three clubs, as well as implied shortness in diamonds or hearts.