Double is the most useful and underused bid in Bridge, as it can be utilised in so many situations that aren’t covered by overcalls. However it is a tricky bid as it has two different meanings, Take-out and Penalty. If you follow these guidelines you won’t go wrong.
Double has two meanings, take-out and penalty. However there is one exception to the above and that is if a player opens 1NT. Then a double by either overcaller is for penalties.
Previously, we learnt that you needed S.O.S to double. However, there are other times when the take-out double is the best bid available.
Protective doubling is when someone has bid and the next two players have passed, ie 1♥ - pass – pass - ?. The bidding is about to end if you pass in 4th position, so you should do everything possible to keep the bidding open.