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How Duplicate Bridge Works
by Cad Delworth

Have you ever wondered how duplicate bridge works in practice, but have never watched a tournament being played? If so, you can see what you've been missing by reading this page.

Introduction

Like trying to describe a spiral staircase without using your hands, trying to explain duplicate bridge to a rubber bridge player who has never seen duplicate being played is notoriously difficult. It took me several years before I felt fully confident that I knew how it worked, and ever since then I've realised how much I still don't know. Many duplicate players, if they're honest, will admit they don't fully understand the mechanical side of duplicate. If that's you, don't worry: no-one's looking, and I won't tell anyone you've come here to find out. :)

What's the Point?

An excellent question. Rubber bridge is an excellent and highly convivial game, and no-one is suggesting you should give it up. Duplicate bridge, however, is the fairest possible way of finding out how good you really are at playing contract bridge. It is just as social as rubber bridge, but it is more strictly regulated than home bridge games, which makes some rubber players regard duplicate as 'cold' or 'unfriendly,' but better descriptions would be 'fair and equal' or 'fiercely competitive.'

What Are the Main Differences?

Rubber Bridge Duplicate Bridge
A game for four players seated at one table. A competition (tournament) for any number of pairs of players, seated at as many tables as needed, usually less than 16. Tables are numbered from 1 upwards.
The players stay in the same seats. NS pairs stay in the same seats; EW pairs move tables after each round.
Needs one or ideally two packs of cards. Needs from 24 up to 32 packs of cards.
Number of hands played cannot be predicted. Number of hands played is fixed at the start of play, usually at least 24.
The actual hands dealt can vastly affect the result. Everyone plays the same hands. 'Good' and 'bad' hands have no effect on the result.
Winning a game makes a pair vulnerable.
Dealer rotates after each hand. 		Vulnerability and dealer of each hand is by hand number, according to repeating 'rota' sequences: none, NS, EW, all; and N, E, S, W.
Each hand is dealt anew. All hands are dealt just before the start of play, then passed around the room in sets.
Bidding is done by speaking out loud. Bidding is done 'silently' using bidding boxes.
Cards played are gathered into tricks. Cards played are kept in front of each player, and are never gathered into tricks.
After play, the four original hands cannot be reformed easily, nor 100% reliably. All four hands are easily picked up after play.
Scores of each deal are totalled on one score sheet. Each deal is scored separately on its own 'travelling' score sheet (traveller) immediately after play.
One or perhaps two players keep the score sheet. As well as the travellers, every player keeps a personal score card containing scores of the hands they have played.
The winners are the pair with the higher points total. Usually, there are two sets of winners, with one ranking for NS pairs and a separate ranking for EW pairs.

In duplicate, the overriding principle is to ensure that every pair has a fair and equal chance of winning. This is why everyone plays the same hands. This is why duplicate has fully road-tested Laws which are strictly and fairly applied by the Tournament Director (TD for short). In short, this is why playing duplicate gives you a better, more accurate idea of how good or bad you are at bridge than playing rubber bridge does.

All these major changes apart, and not forgetting the whole issue of players and boards moving around the room like a slow-motion folk dance, duplicate is the same game as rubber bridge. You bid and play hands just as you would in rubber bridge.

A Few Definitions

There are a handful of terms you will need to know to be able to make sense of the rest of this page. These are:

bidding box


A small box (four per table) containing bidding cards.

Players place bidding cards on the table in front of them instead of speaking their bids.

board
  1. A numbered tray or wallet which indicates vulnerability and dealer, containing labelled pockets for four bridge hands, and a pocket for a travelling score sheet.
    Boards are numbered upwards from 1.
  2. A specific dealt bridge hand, usually referred to by number,
    as in: 'How did you play board 24?'
hand
  1. A single player's bridge hand of 13 cards.
  2. The set of four hands which make up a deal.
relay A set of boards which is not in play during the current round. Relay sets are placed between two tables.
round A timed period of play, during which all players must bid, play, and score all the boards in the set on their table. Usually, there are as many rounds of play as there are tables.
set A group of consecutively numbered boards: usually two, three, or four boards. Players play one set of boards per round. After each round, the set of boards at each table is passed to the next table.
table One of the physical tables. Each table is numbered, starting with 1.
TD Short for Tournament Director, the person who controls the entire event. The TD usually sits North at table 1.
traveller A score sheet for one board, which 'travels' within a pocket in that board, hence its name.

An Example Tournament

The very best way to understand duplicate is to watch a tournament, which I strongly urge you to do, preferably after reading this page. From this point on, I will show you how a tournament for ten pairs (twenty people) would work in practice.

This example tournament uses the most common movement method, called the Mitchell movement after the gentleman who invented it.

Setting Up

Our ten pairs will sit at five tables, which the TD sets up like this:

Table 5
NS 5
EW 10
Boards 21–25
Table 4
NS 4
EW 9
Boards 16–20
Table 3
NS 3
EW 8
Boards 11–15
Table 2
NS 2
EW 7
Boards 6–10
Table 1
NS 1
EW 6
Boards 1–5

Note that each table has the same number of boards: five in this example. The NS pairs take pair numbers of their starting table; the EW pairs add the number of tables—five in this example—to their starting table number for their pair numbers. This gives every NS and EW pair a unique pair number, which they use for the entire tournament.

Before play begins, each table shuffles and deals the cards in each of their boards, placing each dealt hand back into the board it came from. These hands will NOT be re-dealt. Each table now has five boards, each of which contains a freshly-dealt hand.

Round One

The TD makes opening announcements and calls for play to begin. Everyone bids, plays, and scores each of the five boards on their table. North fills in the scores on the travellers, agreeing each one with all three of the others at the table.
For five boards, this should take no more than 38 minutes.

'Move, Please!'

When everyone has played finished playing and scoring their five boards, the TD announces:
'East-West, move when you can for the next round, please!'

Two things then happen at the same time:

  1. Every East-West pair gets up and moves up one table; that is, to the next higher-numbered table. The EW pair at the highest numbered table moves to Table 1.
  2. All the Norths pass their set of five boards down one table; that is, to the next lower-numbered table.
    North at Table 1 passes boards to the highest numbered table.

When this 'musical chairs' exercise has finished, this is the new situation just before round two:

Table 5
NS 5
EW 9
Boards 1–5
Table 4
NS 4
EW 8
Boards 21–25
Table 3
NS 3
EW 7
Boards 16–20
Table 2
NS 2
EW 6
Boards 11–15
Table 1
NS 1
EW 10
Boards 6–10

As before, everyone bids, plays, and scores the five boards on their table and when everyone has done so, the TD calls the next move. After the second move, the room looks like this:

Table 5
NS 5
EW 8
Boards 6–10
Table 4
NS 4
EW 7
Boards 1–5
Table 3
NS 3
EW 6
Boards 21–25
Table 2
NS 2
EW 10
Boards 16–20
Table 1
NS 1
EW 9
Boards 11–15

Take A Break

The TD sees it's about an hour since play began, so announces a break of 20–25 minutes. (This is when it's done at the Carlton: other clubs may take the break at a different point.)

After the break, everyone bids, plays, and scores the five boards on their table and the TD calls another move.

And So On…

After the third move, here is the geography:

Table 5
NS 5
EW 7
Boards 11–15
Table 4
NS 4
EW 6
Boards 6–10
Table 3
NS 3
EW 10
Boards 1–5
Table 2
NS 2
EW 9
Boards 21–25
Table 1
NS 1
EW 8
Boards 16–20

As before, everyone bids, plays, and scores the five boards on their table. There is only one more move to go, so the TD makes closing announcements and calls the last move, resulting in this final diagram:

Table 5
NS 5
EW 6
Boards 16–20
Table 4
NS 4
EW 10
Boards 11–15
Table 3
NS 3
EW 9
Boards 6–10
Table 2
NS 2
EW 8
Boards 1–5
Table 1
NS 1
EW 7
Boards 21–25

The final sets of boards are played and the TD collects all the travellers, enters the scores into the club's scoring program on the computer, and prints out the results.

If you examine the five diagrams carefully, you can check that every pair played all 25 boards: and at no time did any pair encounter any boards they had already played. This simple 'pair up, board down' system will work for any odd number of tables. Hats off to Mitchell!

Even Numbers: Share and Relay

A problem arises if there are an even number of tables, because the movement fails after half the rounds are played, with pairs encountering boards they have already played. You can work this out for yourself on paper if you don't believe me. :)

Luckily, a simple 'double tweak' to the Mitchell movement for an odd number of tables solves this problem:

  1. The highest-numbered table and Table 1 share sets of boards for the entire tournament; and
  2. There is always one set of boards halfway round which is not in play, known as a 'relay' set. This set of boards is usually placed on a side table between the tables either side of it.

Here is how the starting setup would look for six tables, showing just the tables and board numbers:

Table 6
1–4
Table 5
21–24
Table 4
17–20
RELAY
13–16
Table 3
9–12
Table 2
5–8
Table 1
1–4

You can again follow this up for yourself and prove that it works. If you do, remember that Table 1 and Table 6 share boards every time, so on round two for example, they both play boards 5–8, and so on until they both play boards 21–24 in the last round. Also remember that sets of boards pass into and out of the relay, so on round two, the relay set is boards 17–20; and on the last round, the relay set is boards 9–12.

Even Numbers: Skip

For even numbers of tables, there is an alternative to the share and relay known as a 'skip.' In a 'skip Mitchell,' there is no relay set and no shared boards: for the move after half the boards have been played, East-West pairs move up two tables instead of one (just that one time).

Most TDs prefer the share and relay method because this means all-play-all and East-West don't play their first opponents again on the last round.


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