Cash game, center cube. White on roll.

White to play 3-1.

Here’s the same position from the last blog post, but this time White has a different roll to play: 3-1.

Here the choice is a little different from before. The only available hit, Bar/24 6/3*, is now a horrible blunder. It has all the disadvantages of the hits in the last post, but in addition it leaves White stuck on the 24-point, just when White needs to be taking some small risks to get an advanced anchor in Black’s board.

Instead, White needs to enter with the three, Bar/22, which gives him both an escaping number (6) and a threat to make an anchor, and then consider whether 24/23 or 22/21 is his best ace. The former is a little safer since White avoids moving to the point Black most wants to make next (Black’s 4-point). The latter play moves directly to that point, hoping to later grab the best anchor available.

Either play might be right depending on circumstances. Here the circumstances favor moving to the 21-point. To see why, we’ll use a frequently handy trick in these sorts of positions. Find Black’s best non-double that attacks or advances his prime, and see how that number plays on the other side of the board. The right play will often duplicate this number.

After Bar/22/21, Black’s best non-double for advancing his prime is clearly 4-2, which plays 8/4* 6/4. But on the other side of the board, 4-2 is also a great shot, making the 20-point anchor. Eureka — duplication!

Now consider Bar/22 24/23. Black’s best non-double for moving his prime is 5-3, which he would play 8/3* 5/3. But on the other side of the board, 5-3 is pretty useless. Hence the 24/23 play creates a new great number for Black, which isn’t the right idea. So White should just play the simple Bar/22/21.