Type

Action, Optional,
Cooperative,
(Alertable)

Either Partner

Allow partner to either penalize or compete further
Note: Some question wisdom of this convention.

Example: 1C - (1S) - 2C - (2S);
                 P   - ( P) -  X

Balancing

Either Partner

In "passout seat", keep Auction alive by "borrowing"
points from partner

Example: (1C) - P - (2C) - P;
                 ( P) - X

Equal Level Conversion Double
(ELCD)

When the partnership agree to play Equal Level Conversion Doubles (ELCD), the doubler is allowed to have shortness in the Club suit - provided the overcalling doubler has 5 Diamond.  This allows the doubler to rebid Diamonds when partner (advancer) responds in the Club suit - overcaller's short suit.

Example: (1H) - X - (P) - 2C;
               (P)   - 2D

Fisher Lead Directing

Defenders

When opponents' auction is based purely on Notrump bidding, asking partner to lead a Club (or Diamond if Right Hand Opponent made a Stayman call).  Also see Lightner Game Double.

Example: (1N) - P - (3N) - P;
                (  P) - X

Lead Directing

Defenders

When opponents' control auction, lead directing request for lead in Doubled suit or opponent's bid suit

Example: 1N - ( P) - 2D! - X
Request for Diamond lead, where 2D! = Jacoby Transfer to Hearts

Example: 1H - (3S) - P - (3N);
               P  - ( P) - (X)
Requests a Spade, promise to win trick & return Heart

Lightner
(Alertable)

Defenders

When opponents' bid slam, lead directing request for an "unusual lead"

Example: (1C) - (1H) - 2D
                (2H) - (2S);
              (5S) - (6S)
Requests a Heart lead to enable a quick ruff

Lightner Game

Defenders

A double of opponents' Notrump contract based on a long running suit, asking partner to lead their short suit without primary honors.  Also see Fisher Double.

Example: (1N) - P - (3N) - P;
                (  P) - X

Maximal
(Alertable)

Either Partner

After Opponents Bid And Raise (OBAR) in lower suit, show game invitational hand (versus competitive)

Example: 1S - (2C) - 2S - (3C);
                  P -  (P )  - X

Negative

Responder

Find a fit in unnamed suit/s, preference to major/s

Example: 1D- (1H) - X

Negative Double

More videos:
    Negate Doubles,  Day 1     Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Negative Double, Day 2     Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Negative Double, Day 3     Blog  Part 1        BridgeHands Members - login for Part 2 and 3
 

Reopening

Either Partner

Compete for a low-level auction

Example: 1H - (1S) - P - (P);
              X
Avoids opponents' winning a "cheap" auction

Negative Slam

Weaker Side

Example: (1H) - 2S - (4H) - 4S;
                (6H) - X

Competitor wants to sacrifice or punish

Negative Free Bid

Responder

Example: 1H - (1S) - 2C with less than 10 HCP

Reverses the meaning of Negative Double, allowing vigorous competition over opponents' overcall

Penalty Double

Stronger Side

Example: (P) - 1H - (P) - 2H;
               (P) -  P  -  (2S) - 3H;
              (3S) - X
With both opponents passing then bidding 3 Spades in a competitive auction, a 3 level Double would generally be penalty oriented.

When one side shows strength (open/raise) and the opponents either compete at a high level or one opponent makes a high level raise, a double may be for penalty (by partnership agreement)
 

More videos:
    Penalty Doubles,                         Day 1  Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Penalty Doubles & Preempts,      Day 2  Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Penalty Doubles & Environment,  Day 3  Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Penalty Doubles & Environment,  Day 4  Blog  Part 1        BridgeHands Members - login for Part 2 and 3
    Penalty Doubles & Environment,  Day 5  Blog  Part 1        BridgeHands Members - login for Part 2 and 3
 

Responsive
(Alertable)

Responder

After Opponents Bid And Raise & Partner (OBAR) bid or double, show values and support of two unnamed suits

Example: (1H) - 1S - (2H) - X

Snapdragon
(Alertable)

Responder

After 3 suits are bid, double shows 5 in unbid suit
and support for partner's bid suit

Example: (1H) - 1S - (2C) - X
Shows 5 Diamonds & 3 Spades

Striped Tailed Ape

Either Partner

Attempt to have opponents' settle for doubled contract and miss slam, where the opponent will "run like a "Striped Tailed Ape" to their long suit if opponent's redouble!  Obviously, this tactic only works with favorable vulnerability.

Example: (1D) - 1S - (2S!) - 4S;
                 (4N) - P   - (5D)  - X  

Stolen Bid/
Cuebid
(Alertable)

Responder

Reuses the Right Hand Opponent's interference bid
Note - partners agree to play "systems on"

Example: 1N - (2C) - X
Double is "Stayman"

Sucker

Either Partner

Unwise Double, based on honors is worthless (long) suits, likely to be ruffed by opponents

Example: 1H - (1S) - 2D - (3S);
                 4D - ( P) - 4H - (4S);
                 X
Both sides have double-fit, increasing probability to make the contract.

Support
(Alertable)

Opener

Determine 3 or 4 card trump support by opener (since responder may only have 4 trump)

Example: 1C - (1H) - 1S - (2H);
                 X 
Show 3 Spades

Takeout,
Informatory

Overcaller

Find a fit in any of three unnamed suits

Example: (1H) - X

Takeout Doubles

This text will be replaced

Video on:
Takeout Doubles:                                  Blog  Part 1   Part 2   BridgeHands Members - login for Part 3
Takeout Double Responses:                  Blog  Part 1                BridgeHands Members - login for Part 2  
Takeout Double Bidding Continuations: Blog  Part 1    Part 2   BridgeHands Members - login for Part 3

3 Notrump Doubled

Defender

Opponents bid a 3 Notrump game contract or above, partnership doubles have various lead directing possibilities

Example: 1H - (1N) - 2N - (3N);
                 X   -  AP