Gary managed to bear all his checkers in and had even started bearing them off, but you luckily landed a shot and stopped him. You then managed to close him out! You think you’re the favourite, but are you ahead enough to double? If you do, should Gary take?
The cube action for a position like this one can be determined by counting how many checkers have been removed from the board. The table below lists Gary’s (white’s) win percentages as a function of checkers borne off, so long as he has a fast board:
| Number of checkers off | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| Win percentage | 4.5 | 7 | 11 | 15 | 22 | 30 | 39.5 | 51 | 58 | 69 | 76.5 | 84 |
There are no more potential gammons or backgammons to consider, so this information is all that you need to figure out your cube action. You should double so long as Gary has taken off 5 or fewer checkers, and he should take if he has at least 5 off. The doubling window is only 1 checker wide, here. On the other hand, if Gary has 11 or more checkers off, he should be the one to double! You should take so long it’s only 11 and not more.
So the cube action is determined if Gary has fewer than 6 or more than 10 checkers off. What about something between those 2 ranges? For example, what if Gary has 7 checkers off, like below?
It’s too early for us to double, but we would love to double eventually! The rule of thumb here is to have 4 fewer checkers off than our opponent. Since Gary has 7 off, we should only double once we take 3 off, and then Gary can still take.
Further reading:
- A blog post with the win percentages, and other handy rules of thumb.
Next lesson: Score-based cube actions
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