Setup and start

At the start of each round, the dominoes are placed face-side down, shuffled, and each player draws an equal number to form their hands. The actual number drawn depends on the number of players, domino set in use, and rule variation in use. For example, for a 3-player game using the double-twelve set of 91 dominoes, each player draws 15 tiles for their hand, under the 1994 Galt rules.^[5] Dominoes held in a player's hand are kept hidden from the other players.^[6]

Any remaining dominoes are placed to one side, forming the "boneyard". For example, under the 1994 Galt rules, in a 3-player game using the double-twelve set of 91 dominoes, the players collectively hold 45 tiles, leaving 46 tiles in the "boneyard".

Opening the station

The highest double tile is set aside before shuffling the tiles and placed to "open the station", starting the game; e.g., with a standard double-twelve set the double twelve is separated before shuffling and placed in the center of the station hub.^[4][6] In each successive round the next lower double is used until all doubles are used. The double-blank is used for the final round;^[4] however, players may agree to play fewer rounds in a complete game, especially when sets larger than double-nine are used.^[7]

Alternatively, in the 1994 rules written by David Galt, the player who is designated to take the first turn places their highest double in the station to start the game. If the first player does not have a double, the next player opens the station with a double. If no players have a double, each player takes a turn drawing one tile from the boneyard until a double is drawn and used to "open the station".^[5]

The player designated to go first should change with each hand. Galt suggests the first player role should rotate so that each player has an equal number of chances to go first.^[5] Other rule variants suggest alternative methods to select the first player:

• The first player is selected at random, then rotated clockwise.^[4]
• The first player for the first round can be selected by age (oldest or youngest), then rotate clockwise for each following round.^[16]
• Each player draws one tile from the boneyard after shuffling. The player who selected the highest total pip count is designated the first player for that round. The drawn tiles are shuffled back into the pile before drawing hands.^[10]
• The first player is the one who holds the double-12 domino after drawing hands.^[13][15]

Basic rules

1. A legal play is made by matching pip values, i.e., the domino being placed is oriented so the pip value on one end of that domino matches the pip value on the free end of a domino which is already on the table.^[13]
2. A player may choose to play their domino(es) on their private train, any marked public train, or the Mexican Train, which is a common train which remains public throughout the game.^[5][4]
3. There is no option to pass a turn. When the player holds one or more dominoes that can be played legally, at least one domino must be played from their hand.^[5][4]
4. When the player holds no dominoes which can be played, that player must draw one domino from the boneyard and play it if the drawn domino can be played. If the drawn domino cannot be played, or if the boneyard is empty, that player must designate their private train or the side of the station facing them, if no private train has been started, as public, by placing a marker.^[5][4][16]
5. After a double domino, i.e., a domino with identical values on both ends, is played legally, that double must be covered by the player who placed it, meaning that player must immediately play another domino legally next to the double. Responsibility to cover the double passes to each player in turn until the double is covered.^[5][6]

Opening phase

The first player then starts a private train, sometimes known as a personal train, by placing a tile that legally starts from the station by matching pip values to the engine in the station hub, in a direction leading towards their seat. Each player takes a turn, mirroring the first player's first move by playing one tile starting from the station hub in a direction that leads toward their seat.^{[9][12][13][15][14][16]}

In other rule variations, during the opening phase, players may start and build their private trains by using as many dominoes as possible from their hand, radiating out from the station hub towards their seats, instead of placing a single domino. Once each player has built these private trains as long as possible, players then start to take turns, placing one or two tiles per turn using their remaining tiles, until one player has emptied their hand, ending the round.^[5][6]

In the 1994 Parsons rules, each player separates their hand into two categories: "personal train" and "extras", with the "personal train" being the longest possible string of end-matching dominoes starting with one that can be laid into the central station hub, and the "extras" being the leftover dominoes that do not fit into the "personal train". With their first move, the first player may choose to start either their "personal train" or the "Mexican Train", using one of the "extras" that has an end matching the "engine" in the station hub.^[4]

Train building

After the initial opening phase, players take turns placing one or two of their remaining tiles legally on any eligible train, which is either their private train, any public train, or the always-public Mexican Train.^{Basic Rule (BR) 2[5]} Two dominoes may be played only when the first domino played is a double.^{BR 5} Play continues from the first player to the left (clockwise).^[17][18] A player may not pass their turn,^{BR 3} as the boneyard-draw rule^{BR 4} or double covering rule^{BR 5} may require that player to designate their train as public.

A train can be as long as the players can make it; it ends only when all dominoes that could match its endpoint have already been played. As a result, trains can become quite long, especially with an extended domino set. It is acceptable to "bend" the train 90° or 180° to keep the train on the playing surface, as long as it does not interfere with the endpoints of other trains.

Playing doubles

When a double is played, it is placed perpendicular to the train.^[14] After a double has been played, the same player is required to play another domino, which is known as finishing, satisfying, answering, closing, or covering the double. The responsibility to cover the double passes to each player if the preceding player is unable to cover it. Each player who is unable to finish the double is required to mark their private train as public, which is consistent with the same basic rules as if that player was unable to make a legal placement on their turn:^{BR 3,4}

• In general, the second (non-double) domino must be played on the double.^[5][6][9]
• The double may be covered either by a domino already held, or by the domino that is drawn, if no suitable domino is held.^[5][4][14]
• If the drawn domino is unable to cover the double, that player ends their turn and play passes to the next player, who then becomes responsible to cover the double, again either with a domino already held, or with the domino that is drawn.^[5][4][14]
• For any player who is unable to cover the double during their turn, that player's private train is marked as public.^[5][4][14] This includes the private train of the player who initially played the double, if that player could not cover the double, regardless of where the double was played.^[5][4]
• All other trains become ineligible until someone "finishes the double", i.e., normal play may not resume until a domino is played against the double to cover it.^[4][14][10]
• If it is not possible to cover the double because that double is the last domino with that pip value, it does not need to be covered.^[5][6]

For example, if player A placed the double nine (9-9), player A must cover the double by making a legal play with a second domino (e.g., 9-7) to cover the double, or player A's private train becomes public; the next player (Player B) is then responsible for covering the double, and if player B is unable to cover, their train also becomes public and the responsibility to cover is passed to the following player (Player C). Responsibility to cover the double continues to pass repeatedly in this manner (Players D, E, F, etc.) until one player can cover the double; multiple trains may become public due to the double covering rule.^[18]

The playing of doubles and covering requirements are subject to significant variance depending on individual custom and the rules in use, so the basic rules presented here are based on a consensus reading of the different rule sets, biased toward the earliest rules, published in 1994 by Galt and Parsons and updated in 2012 by Bauguess.^[4][5][6] Refer to the § Double variations section in this article for a more specific description of the differences.

Ending and scoring the round

The round ends once one player has placed all their dominoes,^[17][18] or when it is not possible to play another domino and the boneyard is empty.^[4] One variation suggests that as a courtesy, a player holding only one domino should tap the table to indicate the potential end of the round in the next turn, giving the other players a chance to lower their score by playing their highest-valued domino.^[4] Optionally, if a player notices another player who has not announced they are holding only one domino, the latter may be forced to draw two tiles from the boneyard, if it is not empty.^[9]

At the end of each round, the player who emptied their hand receives 0 points, while each of the other players receives the sum of all pips (dots) on the dominoes remaining in their hand. The person with the fewest points after all thirteen rounds have been played is the winner.^[4]

In the case of a tie, the person with the most 0-point rounds is the winner. If this still results in a tie, the person with the lowest round total other than 0 is the winner.^[9]

Example

Partnerships

With four, six or eight players, the game can be played in teams of two, with partners sitting opposite each other. Rules are identical except that a player's train and their partner's train are considered to be a single train, as they will usually extend from opposite sides of the station, and thus a player can play on their own end or their partner's, and neither end becomes public until neither partner can play a tile. Scoring is also handled in pairs, with the player who went out scoring zero for their team (even though their partner will have dominoes remaining) and other teams summing their scores for a team score.

Faster pace

Double variations

Blanks

Blank ends (no pips) are sometimes considered wild cards.^{[citation needed]}

Blanks typically score zero points, but each blank could be scored as 25 points, with the double blank domino scoring 50 points.^[9]