The doubling cube

The doubling cube lets a player raise the stakes when they think they are ahead.

Before rolling, you may double: you offer the cube to your opponent.
Your opponent takes, and the game is now worth twice as much; they own the cube, and only they can double next. Or they drop, and lose the game at its value before the double.
The cube's faces are 2, 4, 8, 16, 32 and 64. Each double moves it to the next.

The cube at 2, on your side: you took a double and own the cube.

When to double, take or drop is the most valuable skill in backgammon. The course's Doubling for beginners is about exactly that; in Choue, see also Double, take and drop.