In rubber bridge, although the better players have a noticable edge and will undoubtedly win in the long run, the outcome of a single rubber depends heavily on which side is dealt the better cards. The idea of duplicate bridge is to eliminate this element of luck, by having the same hands played more than once, by different sets of players.
Suppose we are partners and play a hand of duplicate bridge as North-South. Instead of being rewarded for our absolute score on that hand, our score is compared with those of other players who played the same deal as North-South against other opponents. We win if we score better than other players managed with our cards, and lose if we score worse.
An almost essential piece of apparatus for playing duplicate bridge is a set of duplicate boards, and a pack of cards for each board. Each board contains four pockets marked North, East, South and West in which the cards for the four players are stored. Each board also carries a number to identify it, and has marks showing which of the players is dealer and whether each team is vulnerable or not. The usual marking of the boards is as follows:
Board 1: dealer North; neither side vulnerable
Board 2: dealer East; North-South vulnerable
Board 3: dealer South; East-West vulnerable
Board 4: dealer West; both sides vulnerable
Board 5: dealer North; North-South vulnerable
Board 6: dealer East; East-West vulnerable
Board 7: dealer South; both sides vulnerable
Board 8: dealer West; neither side vulnerable
Board 9: dealer North; East-West vulnerable
Board 10: dealer East; both sides vulnerable
Board 11: dealer South; neither side vulnerable
Board 12: dealer West; North-South vulnerable
Board 13: dealer North; both sides vulnerable
Board 14: dealer East; neither side vulnerable
Board 15: dealer South; North-South vulnerable
Board 16: dealer West; East-West vulnerable
Before the boards are played the cards are shuffled, dealt and placed in the pockets, by a neutral person or by a player in the presence at least one opponent. Alternatively the cards may be dealt by computer, with the aim of ensuring perfect randomness. Generally, the computer produces printed slips (curtain cards) which specify which cards should be in each hand on each board; a neutral person then has to construct the hands according to the curtain cards and put them in the pockets. It is also possible for the playing cards to be physically sorted and placed in the boards by a machine controlled by the computer.
When about to play a board, the players take their cards from the appropriate pockets, check to see that they have 13 each, and then bid as usual. The mark on the board showing the 'dealer' in practice just indicates which player is to begin the bidding. During the play, the cards are not played in the centre of the table but in front of the players. At the end of each trick, all four players turn their played card face down. It is customary to overlap the played cards, with the longer axis of the card pointing to the winners of the trick (i.e. the cards belonging to tricks you have won are placed upright from your point of view, and the ones belonging to lost tricks sideways). That way you can easily see how many tricks you have won. Also, if the cards are kept in order, any dispute about revokes can be settled by reconstructing the play. At the end of the play, each player's cards are replaced in the correct pocket, ready for the next time the board is to be played.
Because duplicate bridge depends on comparing the results on individual boards, it is necessary that each group of players who play a board should start from the same position. Therefore it is not practicable to play rubbers, in which scores are carried forward from deal to deal and affect the tactical situation. Instead, each board is scored in its own right, and does not affect the scores for subsequent boards.
The concept of vulnerability is however retained. Each board is marked to show whether both sides, one side or neither side is vulnerable for that board. You still need to score at least 100 points for tricks bid and made to make a game, but on each board, both sides start with zero points towards games - there are no 'part scores' carried forward.
In place of the rubber bonus, there are game and part score bonuses:
Making a game when vulnerable: 500 points
Making a game when not vulnerable: 300 points
Making a part score any time: 50 points
The rest of the scores are the same as in rubber bridge. So for example:
if we bid 2 spades and make 4 (10 tricks) we score 170, that is 60 for two spades bid and made, 60 for two overtricks and 50 for the part score;
if we bid 4 spades and make it when we are not vulnerable we score 420 (120 for the contract and 300 for the game);
if we bid 4 spades and make it when we are vulnerable we score 620 (120 for the contract plus 500 for the game).
These scores are of course not yet the final scores. They have yet to be compared with the scores achieved by other people who have played the same cards as us on this board. The method of doing this comparison varies according to what kind of duplicate is being played. Perhaps the commonest types are teams of four with international match point (imp) scoring, and match pointed pairs.
Teams of Four
A match can be played between two teams of four - eight players in all. Each team consists of two partnerships, and you need two tables - preferably in separate rooms so that players cannot overhear events at the other table. Before starting the players agree how many boards will be played - this could be 24, 32, 48 or more, depending on the seriousness of the match and the time available. A 24 board match should easily be completed within three hours.
Call the tables 1 and 2 and the teams A and B. Then the pairs of team A sit North-South at table 1 and East-West at table 2, and the pairs of team B occupy the other seats. Take a convenient number of boards - say boards 1 to 12 - and give the first 6 to table 1 and the other 6 to table 2. As each table finishes their 6 boards they pass them to the other table to be replayed. When all 12 boards have been played at both tables, it is a convenient time to have a break and compare scores.
It may be agreed that for the next session, the two pairs of one one of the teams should swap places. This gives each pair the opportunity to play against both pairs of the opposing team. The procedure about the number of sessions in a match and the choice of seats for each session may be laid down by the organiser of the event - otherwise it needs to be agreed between the team captains.
Each player should have a scorecard to record the score on each board. The card has a row for each board. The beginning of North's card from table 1, when completed, might look like this:
Board Final Score IMPs
Deal # Vul Contract By Tricks Plus Minus Plus Minus
N 1 - 4S S 10 420
E 2 NS 5D* W 8 500
S 3 EW 3NT W 12 690
W 4 All 2H N 9 140
In the contract column 5D* means 5 diamonds doubled. The 'By' column shows who was declarer. The score is recorded from North's point of view - so when West goes down in 5 diamonds it is positive. The IMPs can only be filled in when this card is compared with one of the cards from the other room. Suppose that our team mate East on table 2 has a card like this:
Board Final Score IMPs
Deal # Vul Contract By Tricks Plus Minus Plus Minus
N 1 - 4S S 11 450
E 2 NS 4H N 10 620
S 3 EW 6NT W 12 1440
W 4 All 4H N 9 100
Now the differences can be converted to IMPs for the team. The following standard table is used:
Point difference IMPs
0 - 10 0
20 - 40 1
50 - 80 2
90 - 120 3
130 - 160 4
170 - 210 5
220 - 260 6
270 - 310 7
320 - 360 8
370 - 420 9
430 - 490 10
500 - 590 11
600 - 740 12
750 - 890 13
900 - 1090 14
1100 - 1290 15
1300 - 1490 16
1500 - 1740 17
1750 - 1990 18
2000 - 2240 19
2250 - 2490 20
2500 - 2990 21
3000 - 3490 22
3500 - 3990 23
4000 or more 24
So in the example, on the first board the difference between the two tables was 30 against us, and we lose 1 IMP. On the second board we lose 3 IMPs. Although on table 1 we defeated West's 5 diamonds, on table 2 with the same cards we allowed North to play and make 4 hearts. On board 3, where we bid the small slam on table 2, while they stopped in game on table 1, we gain 13 IMPs for a 750 point difference. On board 4 both Norths made 9 tricks in hearts, but we gain 6 IMPs because we just bid 2 hearts rather than 4. Overall we are 15 IMPs up on those four boards.
After each scoring interval, the captains of the teams should check that the scores agree. The purpose of every player keeping score is to make it easier for errors to be traced and corrected.
At the end of the match, the result is the difference in IMPs between the teams. Sometimes there is then a further conversion of this margin into a match result, in which some fixed number of victory points is apportioned between the teams. There is no standard conversion table, but here is an example table for a 24 board match:
IMP difference Victory Points
0 - 2 10 - 10
3 - 6 11 - 9
7 - 11 12 - 8
12 - 16 13 - 7
17 - 21 14 - 6
22 - 27 15 - 5
28 - 33 16 - 4
34 - 39 17 - 3
40 - 46 18 - 2
47 - 54 19 - 1
55 or more 20 - 0
In the example, if we were still 13 IMPs ahead having played 24 boards, using this table we would win the match 13-7. If the match was part of some larger competition, such as a league, then we would score 13 victory points and our opponents would score 7.
There are also events in which many teams of four compete. There are various ways of organising these. At any particular time in such an event you will be playing a part of a match against some other team, and at some time your team-mates will play other cards of the same boards against the other half of that same team. The scores are eventually compared to find how many IMPs you won or lost against that team.
This is the game most usually played in Bridge clubs, and there are also many tournaments organised this way. As implied by the name, it is played between a number of fixed partnerships or pairs. For a pairs event you need a minimum of three tables (6 pairs, 12 players), and it works better with more players - say 10 tables (40 players) or more.
Generally you play two or three boards at a table - this is called a round - and then one or both pairs move to another table and play other boards against other opponents. The movement will be organised by the director in such a way that no one ever plays boards they have played before, or against opponents they have played before.
The score for each hand is recorded to a travelling scoresheet, which is kept in the board. None of the players may look at this sheet or take it out of the board before the board has been played. North is then responsible for entering the result and showing the completed sheet to East-West to check that it has been done correctly. Each pair has a number to identify them, and this must also be entered on the scoresheet, to show whose result it is. North is also responsible for the movement of the boards - checking at the start of the round that the correct boards are being played and passing them on at the end of the round.
At the end of the whole session, each scoresheet will contain the results of all the pairs who have played that board. The scoresheets are then collected by the organisers and the scores compared. Each pair is awarded 2 match points for each pair who scored worse than them on that board, and 1 match point for each pair who scored equally.
A completed score sheet might look like this:
Board No. 1
Pair No. North-South Match points
NS EW Contract By Tricks Plus Minus NS EW
1 8 4S N 10 420 5 7
2 13 3NT S 10 430 8 4
3 11 5C* E 8 500 12 0
4 9 4S N 10 420 5 7
5 14 4S N 11 450 10 2
6 12 5S N 10 50 0 12
7 10 3S N 10 170 2 10
Then the total match points scored by each pair over all the boards are calculated. This is generally converted to a percentage for each pair of the points they scored compared to the theoretical maximum. This gives a fair comparison between pairs who have played different numbers of boards. The winners are the pair with the highest percentage. There may be prizes for 1st, 2nd, 3rd place, etc.
Sometimes the movement is such that the North South pairs stay put and the East-West pairs remain East West throughout. In this case the results for the East-West pairs and the North-South pairs are separate, and there are two winning pairs. To enable all the pairs to be placed in a single ranking order, the last round is sometimes played with an arrow switch. This means that the players who were previously North-South play the East-West cards for that round and vice versa.
Duplicate bridge procedure and ethics
During a duplicate event, where play will be in progress at several tables at the same time, it is important that players to not see, overhear or otherwise take an interest in the play at the other tables. Any attempt to do so would be cheating, as it might give unauthorised information about the distribution of cards or the result of a board which the player would later be playing. For similar reasons, partners should not discuss the boards they have played in the hearing of other players until the end of the event (or a suitable break at a time when everyone has played the same boards).
In some places devices are used to enable the bidding to proceed silently, reducing the chance of hearing bids from another table. The best arrangement is for each player to have a bidding box, which is a box containing cards displaying all the possible bids, pass, double and redouble. At your turn to bid you display the relevant card. All the cards used for bids remain on view until the end of the auction, thus also avoiding the problem of players forgetting or mishearing part of the bidding. A cheaper but less satisfactory method is to use a large card with a compartment for each possible bid; at your turn you point to the bid you wish to make.
In an event of any size, there will be a tournament director whose job is to ensure that the play flows smoothly. This person will deal with any infringements of the rules that occur, referring when necessary to the laws. If some irregularity occurs, such as a bid out or play out of turn, an illegal bid or play, or discovering that the cards have been wrongly boarded (the hands contain more or fewer than 13 cards), the director should be called to the table. This should not be construed as an accusation of cheating - the purpose of calling the director is simply to ensure that the irregularity is sorted out fairly and in accordance with the rules. The instructions and decisions of the director should be followed and respected at all times. In a serious tournament, if you strongly disagree with the director's ruling, it should be possible to appeal against the director's decision. The procedure for this varies according to the nature of the event - the director should be able to advise you on the options.
Stop and alert
In tournament bridge, if you make a bid at a level higher than necessary in that denomination (a "jump" bid), you are supposed to precede your bid by saying "stop" (or displaying your "stop" card if you are using bidding boxes). The next player must then pause before bidding or passing. The reason behind this is that after a jump bid the next player may have reason to hesitate, as your unexpectedly high bid might have disrupted the course of action which that player was planning. The player is forced by the stop rule to hesitate anyway, so avoiding giving unauthorised information. Example:
North bids "one heart"
East bids "stop; four spades"
South pauses and then passes
As South was forced to pause, North gets no clue as to whether South would have bid if it were not for East's interruption.
When a player makes an artificial bid, the partner of the bidder alerts the opponents to the fact that the bid is artificial, by saying "alert", displaying the "alert" card if using bidding boxes, or knocking the table. The rules as to which bids are regarded as artificial and need to be alerted vary somewhat from place to place.
This is information which you obtain as a result of some irregularity in the game, rather than as a legitimate deduction from the bidding and play. Unauthorised information might arise from:
hesitation or undue haste in bidding or playing a card
seeing another player's cards
extraneous remarks made during the game; questions about the bidding or play; also gestures, tone of voice, etc.
seeing or overhearing events at another table
The principle is that you are allowed to take advantage of anything done by your opponents at your table, but you are obliged to ignore any unauthorised information gained from your partner's actions or other tables.
In fact if you do obtain unauthorised information from your partner, you should not only ignore it but be prepared to prove that you have done so. This means that if you are involved in any kind of close decision you ought to take the action opposite to the one indicated by the information from your partner. For example if during the bidding your partner passes after a hesitation, you must pass too unless you have a cast iron case for bidding, otherwise you might be accused of making use of the unauthorised information that your partner nearly had a bid.
In bridge it is illegal to behave deliberately in such a way as to try to give spurious information to the opponents. For example if you have only one card of a suit that is led, it is illegal to hesitate before playing it, creating the impression that you had more than one card to choose from. On the other hand there is no ban on making deceptive bids and plays to confuse the opponents - as long as these are not part of an undisclosed partnership agreement. You are free for example to play a card different from what might be expected from your holding, as long as you do it smoothly and without comment. Similarly you are free to make a bid which is inconsistent with your system to upset the opposition, provided that this is as much of a surprise to your partner as it is to the opponents.