The Double Blank Rule

The 0-0 domino causes more arguments than the rest of the set put together. By a plain pip count it is worth nothing, and yet it is the single hardest tile to get rid of. Most families fix that with a penalty — but they do not agree on how big. Here is what the common versions are, and why the rule exists at all.

The problem the rule solves

Scoring in Mexican Train counts the dots left in your hand, so a tile with no dots costs you nothing. That is fine right up until you look at what the double blank actually does in play.

A 0-0 can only be played on a train whose open end is a blank. Blanks are the rarest useful number to see on an open end, so the tile sits in your hand for the whole round. Every other double at least matches something people are playing. This one usually does not, and it is free to be caught with. So under a strict pip count the hardest tile in the game carries no risk — which feels wrong to almost everybody who plays it a few times.

The three common conventions

Convention	Double blank scores	What it does to the game
Strict pip count	0 points	The rules stay simple and consistent. Nobody minds holding the blank, so it rarely moves.
Moderate penalty	25 points	Roughly a heavy double. Enough to make you want rid of it without wrecking a round.
Full penalty	50 points	Larger than any real hand. Being caught with it usually decides the round outright.

Fifty is the version most people mean when they say "the double blank rule". It is dramatic, and it turns the tile into a hot potato — which is exactly the point. Twenty-five is the quieter choice and, if your table has never used a penalty before, the easier one to introduce.

What a 50-point penalty does to a round

Consider a typical hand at the end of a round: three or four small tiles, maybe fifteen points in total. A 50-point penalty is more than three times that. It means one player can lose a round they were otherwise winning comfortably, purely because they never saw a blank open up.

That is worth knowing before you agree to it. The penalty adds a real edge to the endgame — people will play a blank on a train they would rather not open, just to be rid of it — but it also adds variance. A group playing for bragging rights over thirteen rounds will barely notice. A group playing three rounds may find one tile decided the whole thing.

Settle it before you deal

Whatever your table prefers, agree it out loud before the first round rather than when somebody is caught. This is the single most common source of "that is not how we play" in the middle of a game, and it is entirely avoidable.

How it works in the online game

At mexicantrain.online this is a setting called Double-Zero Penalty, chosen when the game is created. It runs from 0 to 50 in steps of five, so 25 and 50 are both there, along with anything in between if your family has landed somewhere unusual. The default is 0 — a strict pip count.

It is set by whoever creates the game and applies to everyone in it, and like the other rules it is fixed once play starts. The scoring then happens automatically: if you are caught with the 0-0, the penalty is added for you and shows up in the round results, so there is nothing to remember and nothing to argue about.

If you are new to the whole game rather than just this rule, start with how to play Mexican Train.

Keep reading

• How to play Mexican Train — the whole game
• How scoring works, with a worked example
• House rules and variations
• Doubles, covering and Blake’s rule