Maximal Double - Opener doubles once a fit is established to show maximal points 15+
Responsive Double - Partner doubles and opponents raise their partners suit, responders double of a major shows both minors, Double of a minor shows both majors
Double and bid another suit show 17+ HCP
Reponders Double
Without game values established - First double is always negative double. Any double after a pass or a bid suit is for penalty. A second double after a negative double is forcing unless you can convince yourself it is penalty
If responder doubles and then shift suits it is game force
Game Values Double
Once Game values established - Partner with shortness in opponents suit must double
Partner should correct if they lied about points or all his quick tricks are in their short suit
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