(Down - Top)
BR 13.1 - Vulnerable and Not Vulnerable
Before explaining the principles of Preemptive bidding, it is necessary to understand two more aspects of the game, vulnerability and the penalty double.
Vulnerability is an aspect of the game used in the original Rubber bridge style of play, where a side becomes vulnerable after having reached a certain score level.
In modern Duplicate Bridge this aspect has been maintained in an artificial way, where the Vulnerability of a side rotates from one board to the next.
For example on Board 1 no side is vulnerable, on Board 2 North South are vulnerable, on Board 3 East West, and on Board 4 both sides are vulnerable.
The entire sequence is set by the International Bridge federation. It runs over 16 boards an then is repeated for each next set of 16 boards (see Scoring).
The Vulnerability is indicated on each individual board, usually by a circular red dot
Vulnerability of a side raises the stakes in terms of points scored for a contract considerably. The trick points score and part score bonus remain the same, but
- the bonus points for a Game contract is raised from 300 to 500 points
- the bonus points for a Small Slam are raised from 800 to 1250 points
- the bonus points for a Grand Slam are raised from 1300 to 2000 points
- Down tricks too are penalised heavier, 100 points per down trick instead of 50
(Down - Up - Top)
BR 13.2 - The Penalty Double
If a player believes the Opponents have bid a contract which they can not make he can "Double" when it is his turn to bid. Like each other final bid, A Double must be followed by a "Pass" from each of the other three players before it is locked in as the final bid.
For example :
| North | East | South | West |
| 1 S
| Pass
| 2 S
| Pass
|
| 4 S
| Pass
| Pass
| DBL
|
| Pass
| Pass
| Pass
| -
|
The Double raises the stakes in terms of points scored at the end of the game.
If the contract is indeed defeated each down trick is worth considerably more to the opposition.
For example :
| Down tricks | Not Doubled | Doubled
Not Vulnerable | Doubled
Vulnerable |
|---|
| 1 Down
| 50
| 100
| 200
|
| 2 Down
| 100
| 300
| 500
|
| 3 Down
| 150
| 500
| 800
|
If, on the other hand the Declarer manages to make his contract his side too will receive a much higher score.
Each trick made receives double the amount of trick points, plus 50 extra bonus points ("for the insult").
If, as a result of the Double the trick points come within the range of a Game or Slam contract the Bonus points for that are also added to the total score.
- For example (Not Vulnerable) :
- 2♦ DBL and made = 2 x 2 x 20 (trick pts) + 50 (part score bonus) + 50 (for the insult) = 180 pts
- 2♥ DBL and made = 2 x 2 x 30 (trick pts) + 300 (game score bonus) + 50 (for the insult) = 470 pts
Any overtricks made too score additional bonus points, 100 pts per overtrick when not vulnerable and 200 pts per overtrick when vulnerable.
If the Declaring side, despite the "Double", are convinced they will make their contract they can "Redouble" Opponents Double. This raises the stakes even more.
The Redouble is locked in as the final bid after three successive Passes.
| North | East | South | West |
| 1 S
| Pass
| 2 S
| Pass
|
| 4 S
| Pass
| Pass
| DBL
|
| RDBL
| Pass
| Pass
| Pass
|
Part score contracts of 1 or 2 are rarely Doubled for penalties.
Instead Doubles at these levels are usually made for Take Out.
A take out Double is made by player who has 12 points or more but, after the Opponents have opened the bidding, has no proper bid to make (see 
