Therefore double shows scattered values with at least 6 points and interest in locating a fit. If the opponents are bidding a minor suit, a responsive double asks partner to pick a major suit. If the opponents are bidding a major suit, a responsive double requests partner to choose a minor suit. He should make a responsive double to ask partner to bid a major. Note that a double by advancer is responsive only when the opponents have opened a one-bid and raised it.
Some players also use the responsive double when partner has made a simple overcall in a suit.
You open 1H and hear LHO pass. This lets them bid 2S to show a four-card raise. When the opponents bid and raise a suit, support doubles are also on. Finally, support doubles also apply when RHO makes a takeout double rather than a simple overcall. Promises 12-14 points with three spades.