Any number may play, but only one player - the "caster" - has the dice at any one time.
In each round, the caster throws two dice until a number between 5 and 9 inclusive appears: this is the "main". Once the main is set, they then throw two dice again.
If they roll the main, they win (a "nick").
If they roll a 2 or a 3, they lose (an "out").
If they roll an 11 or 12, the result depends on the main:
with a main of 5 or 9, they throw out with both an 11 and a 12;
with a main of 6 or 8, they throw out with an 11 but nick with a 12;
with a main of 7, they nick with an 11 but throw out with a 12.
If they neither nick nor throw out, the number thrown is called the chance. They throw the dice again:
if they roll the chance, they win;
if they roll the main, they lose (unlike on the first throw);
if they roll neither, they keep throwing until they roll one or the other, winning with the chance and losing with the main.
The caster keeps their role until losing three times in succession (throwing three "outs"). After the third out, they must pass the dice to their left, that player becoming the new caster.
Bets are made between the caster and the house's banker. If the caster nicks on the first throw after setting the main, they win an amount equal to their stake. After the first throw, the caster wins their stake if they get their chance before their main. An out means the player loses their stake.
After the first throw, the caster (and other players, via side bets) may wager an additional sum that the chance will come before the main. These bets are made at odds determined by the relative proportions of the main and the chance:
Main Chance
4 5 6 7 8 9 10
5 4/3 — 4/5 2/3 4/5 1/1 4/3
6 5/3 5/4 — 5/6 1/1 5/4 5/3
7 2/1 3/2 6/5 — 6/5 3/2 2/1
8 5/3 5/4 1/1 5/6 — 5/4 5/3
9 4/3 1/1 4/5 2/3 4/5 — 4/3
For example, with an odds stake of 10 gp, a main of 7 and a chance of 5, a caster stands to win 15 gp (3/2 x 10); with the same stake, a main of 5 and a chance of 6, they could win 8 gp (4/5 x 10).