Conventions in depth
After an opponent overcalls partner’s opening, responder’s double is for takeout and shows the unbid suits.
Partner opens, the next hand overcalls, and the natural bid you wanted, often a new major at the one level, is suddenly gone or pushed too high. Rather than waste the double as a rare penalty threat, the partnership agrees it is takeout: responder’s double shows the values and the unbid suits the overcall would otherwise have silenced. The focus is on finding a major-suit fit, but you must also be ready for partner to name the other unbid suit.
BidMaestro plays negative doubles through 2♠; above that a double is for penalty. The double needs about 6 points over a one-level overcall and roughly 8–10 over a two-level overcall, a couple more when vulnerable. Which suits it shows depends on the auction:
The awkward hand is the one that is long and strong in the suit the opponent overcalled, exactly the hand that used to want a penalty double. You cannot double, because that would be takeout and partner could not leave it in. Doubling with a strong holding in their suit is the most common error with this convention.
The solution is a trap:
Opener has some discretion: with a light opening facing a partner who had already passed, opener need not reopen.
The guiding idea: the double no longer says “I can beat them.” It says “I have the other suits and the values to compete. Help me place the contract.” The penalties still happen, but through the trap pass and opener’s reopening double, not a direct double.