In a priming battle Blue has three jobs at once, extend the prime, bring the back checkers to the edge of White’s prime, and deny White the same. The race is level at 146 to 143, Blue holds the 4, 5 and 6 points with a slot on the 7 point, and White holds the 17 through 20 points with an anchor on Blue’s 1 point. Blue plays 24/22 13/8. From the 22 point a 6 leaps the prime next turn and lands on White’s blot on the 16 point, and the new checker on the 8 point adds cover for the slot. The slot faces 15 shots from the anchor, a fair price for the bar point. Lifting the slot with 24/22 7/2 buries a checker on the 2 point, where it blocks nothing, and still leaves it open to 11 shots. It loses 0.168 equity, a BLUNDER.

Blue should keep building the prime, because the side behind in the race holds the timing. Blue trails by 32 pips, 148 to 116, but White’s blot on Blue’s 1 point sits behind the 4 through 7 points, and White’s own board holds only the 19, 20 and 21 points. Blue plays Bar/23 13/11 13/9, anchoring on White’s 2 point and making the 9 point for five blocking points. A prime grows from the back, and the builders on the 8 and 11 points are placed to fill the 8 point for a full six-point prime. The blots face 13 shots, and the worst case is re-entering against a three-point board with timing to spare. Playing safe with Bar/23 13/9 8/6 strips the 8 point and leaves no builder behind the prime, so White’s checker gains time to escape. It loses 0.168 equity, a BLUNDER.

Blue is priming, and extending the wall from four points to five comes first. Blue trails by 9 pips, 133 to 124, holds the 4 through 7 points with a spare on the 4 point, and White’s last checker sits on Blue’s 1 point. Blue plays 13/9 4/3, covering the 3 point with the spare for a five-point prime from the 3 point to the 7 point and bringing a builder to the 9 point. The 3 point takes away White’s 2s, so the trapped checker now moves only with an ace, and the 8 and 9 point checkers both bear on the 8 point, the back of the prime, where the sixth point will be made. Covering with 8/3 makes the same five points but spends the builder that was going to make the 8 point, so the prime stops growing. It loses 0.122 equity, a BLUNDER.

Blue should attack the inner board while White is on the bar, because every point Blue closes now is a roll White spends dancing. Blue leads by 17 pips, 106 to 123, holds the 2 and 4 through 7 points with a safe anchor on White’s 5 point, and White has one checker on the bar against them. Blue plays 7/3 4/3, making the 3 point for a five-point board from the 2 point to the 6 point. White now enters only with an ace, 11 rolls of 36, and every dance is another turn in which White’s own prime must move while Blue’s structure stands still. Running with 20/16 8/7 covers the bar point but breaks the anchor, leaves blots on the 16 and 20 points facing 16 shots, and lets White enter with 20 rolls instead of 11. It loses 0.167 equity, a BLUNDER.

Blue is priming, and the hit that also makes a point is the one to play. The race is level at 109 to 112, Blue holds the 4 through 8 points, and White’s blot on Blue’s 3 point is the checker that keeps White’s game alive, since White’s five points from the 17 point to the 21 point trap Blue’s last checker, and left alone it escapes with any 6. Blue plays 6/3* 5/3, hitting and making the 3 point for a six-point prime from the 3 point to the 8 point. White enters only on the 1 or 2 point, 20 rolls, and then cannot move until the prime breaks, so White’s prime must crack first. Hitting loose with 24/22 6/3* leaves the blot on the 3 point open to 14 return shots and moves the back checker nowhere useful. It loses 0.258 equity, a BLUNDER.

Blue should complete the six-point prime and spend the rest of the roll on timing, because the side that runs out of spares breaks first. The race is level at 95 to 95, White has a checker on the bar, and Blue’s last checker is held behind White’s five points from the 18 point to the 22 point. Blue plays 12/7 4/1, covering the bar point for a prime from the 2 point to the 7 point and playing the 3 with a spare. The checker left on the 8 point is Blue’s timing, a spare that moves later without touching the prime, and the worst case, an entering ace that hits the blot on the 1 point, only hands Blue a checker to recirculate. Playing 12/7 8/5 moves the last spare inside the prime, so the next awkward roll breaks a point. It loses 0.143 equity, a BLUNDER.

Blue is behind in the priming battle, and the side that is behind should hit rather than build. Blue trails by 8 pips, 132 to 124, holds six scattered points without a prime against White’s five points from the 16 point to the 20 point, and White has blots on Blue’s 5 and 10 points. Blue plays 11/10* 8/5*, putting two White checkers on the bar. One loose hit in the inner board would leave Blue exposed, and the more exposed the hitter, the more the second hit matters. White must spend whole rolls entering, White’s prime decays meanwhile, and Blue’s gammon chances rise to 15 percent. Hitting and making the 5 point with 8/5* 6/5 leaves the second blot free and lets the one checker on the bar enter with 20 rolls. It loses 0.128 equity, a BLUNDER.

Blue should convert the prime into an attack, because the prime has done its work and the checker in front of it is the target. Blue leads by 32 pips, 100 to 132, holds a six-point prime from the 3 point to the 8 point, and White’s lone checker sits on Blue’s 1 point, where it cannot move until that prime breaks. Blue plays 8/1*, hitting off the front of the prime and giving up the 8 point to do it. White enters with 20 rolls and otherwise dances, every dance costs White timing, and Blue’s gammon chances climb above 26 percent. The checker left on the 8 point faces only 2 shots. Clearing safely with 8/5 8/4 keeps five blocking points too, but it leaves White’s checker in place while Blue’s own back checker runs short of time. It loses 0.112 equity, a BLUNDER.

Blue should switch from priming to running, because the side with fewer pips has less timing and must not be the one forced to break first. Blue leads by 15 pips, 135 to 120, holds the 4 through 8 points, and has two checkers on White’s 2 point behind White’s 19 through 22 points, while White owns the cube at 2 and has anchored on Blue’s 3 point. Blue has only two spares outside the prime, so a quiet turn or two would force Blue to break points in front of White’s anchor. Blue plays 23/15, bringing one back checker out past the prime while the gaps on the 16 and 18 points are still there. The outfield blots face 5 shots. Building with 13/8 10/7 is perfectly safe but spends both spares at once, after which every roll comes out of the prime. It loses 0.107 equity, a BLUNDER.

Blue is far behind in the race and trailing in the priming battle, and the side that trails should jump the prime and hit rather than build. Blue trails by 50 pips, 153 to 103, holds the 4 through 8 points with three checkers on White’s 4 point, and White’s blot on Blue’s 3 point is White’s only checker outside home. Blue plays 21/15 6/3*, jumping White’s prime with one anchor checker while the anchor stays, and hitting the blot before it escapes with a 6. White enters with 27 rolls but stays behind five blocking points, and Blue’s gammon chances rise from 7 to 11 percent. Running quietly with 24/15 leaves White’s checker free to escape with any 6, and Blue has no race as a fallback. It loses 0.062 equity, an ERROR.