Contract Bridge : DOUBLE - VULNERABLE

What does Vulnerable mean - When to use IMPs

SC 1.1 - What do DOUBLE and REDOUBLE mean ?

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 downtrick 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 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) :: 2D DBL and made = 2 x 40 (trick pts) + 50 (part score bonus) + 50 (for the insult) = 180 pts; 2H DBL and made = 2 x 60 (trick pts) + 300 (game score bonus) + 50 (for the insult) = 470 pts

Any overtricks made too score an additional bonus.

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 Lesson on Take Out Doubles).

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SC 1.2 - What does VULNERABLE mean ?

Vulnerability of a side too raises the stakes in terms of points scored for a contract considerably.

This aspect of the game was used in the original Rubber bridge style game, where a side became vulnerable after having reached a certain score level.

In modern Duplicate bridge this aspect has been maintained in an artificial way by designating the Vulnerability of a side on each board played as follows :

ROTATION of VULNERABILITY

Board Dealer Vulnerable Board Dealer Vulnerable

1 & 17 N None 9 & 25 N East-West

2 & 18 E North-South 10 & 26 E All

3 & 19 S East-West 11 & 27 S None

4 & 20 W All 12 & 28 W North-South

5 & 21 N North-South 13 & 29 N All

6 & 22 E East-West 14 & 30 E None

7 & 23 S All 15 & 31 S North-South

8 & 24 W None 16 & 32 W East-West

For boards 17 - 32 (and boards 33 - 48) the sequence as for boards 1 - 16 is repeated

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SC 1.3 - When to use IMP scoring

International Match Points (IMPs) are used in competitions between two or more Teams.
Each Team consists of 4 players. Two of the players form a NS pair, the other two form an EW pair.

With two Teams playing against each other, the NS pair of Team 1 plays against the EW pair of Team 2 on one table.
On the other table the NS pair of Team 2 plays against the NS pair of Team 2.
This way both teams cover all 4 hands of each deal.

Halfway the match one Team may switch its pairs from EW to NS and visa versa, so that all four players of each team play against all players of the other team.

At the end of the match the point score for each board is added up and the total converted into International Match Points.

Board	Contract	NS - T1	EW - T1	Total T1	IMPs for T1	NS - T2	EW - T2	Total T2	IMPs for T2
1	3NT	430	-400	30	2	400	-430	-30	-
2	4S	-420	-50	-470	-	50	420	470	10
3	3D	110	-110	0	0	-110	110	0	0

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