Reasons for Slotting To make a point that would be difficult to make naturally To unstack heavy points To utilise sparse resources effectively To reduce a game to a one-roll proposition
Magriels Principles - Tactical Do you have an advanced anchor? Having an advanced anchor enables you to play boldly. How strong is your opponents home board? The stronger your opponents home board, the more conservatively you must play. How strong is your home board (especially compared to your opponents)? If you have more home board points than your opponent, you tend to play boldly; with fewer points closed, more conservatively. Does your opponent have blots in his home board? If your opponent has blots in his home board, you can afford to take more chances because of possible return shots.
Magriels Principles - Strategic How many checkers do you have back? The more checkers you have back, the more chances you can take. With no checkers back, or only one checker back, you must play conservatively. How many checkers does your opponent have back? When you opponent has no checkers back or only one checker back, you want to play provocatively to force an exchange of hits.
Other Key General Principles Put your checkers where you want them When in doubt, hit Prime an anchor; attack a blot When ahead in the race, race
The Opening Roll – Black to Play 21, 41 or 51 Correct Play: Your choice!
Commentary In the opening the bots will tell you there is always a best move but it is largely a question of style and what you feel comfortable with so play whatever you prefer. For the record the bots preferences are to slot with 21 and split with 41 or 51. Certain match scores will dictate whether to slot or split. When trailing you should prefer to slot and when leading to split.
Commentary Once the opening roll has been made you dont have so much choice. There is nearly always a best move in response. When you opponent has brought down builders it is nearly always correct to slot with 21, 41 and 51 in response. The reasons are: It duplicates some your opponents numbers It unstacks a heavy point Your opponent now has more checkers in the zone so if you split a blitz attack by your opponent becomes a possibility The equity differences are relatively small but big enough that you should learn to slot in these situations.
And slightly later ….. Correct Play: bar/21, 6/5
Commentary Here black is further behind in the race. Reject bar/24, 13/9 – an awful move that does virtually nothing to improve your position The four is played bar/21 The one can be played 6/5 or 24/23 As in the previous position, 6/5 is the correct play It duplicates some your opponents numbers It unstacks a heavy point The anchor on the 24-pt protects against a blitz Bar/21, 24/23 is a common misplay in this type of position – learn to avoid it.
Opening Summary Opening roll slot is optional (except in certain match play situations) The response to the opening roll is not optional When behind in the race early on slotting becomes more attractive
Commentary This and the next position are from from Barclay Cookes Paradoxes and Probabilities. Of the 168 problems in he book, 44 of them have solutions that are blunders! In the 1970s pure play was the order of the day! The trick here is to find the Cooke move Cooke suggested 13/10, 6/5 - a move that does nothing to meet the demands of the position! The front checkers are well positioned – time to get the back men going with 24/21, 24/23 while white has only eight checkers in the zone and a disjointed position.
Commentary Here Cookes solution is even worse – 13/7, 5/4. Purity for puritys sake! This is a huge equity error We have learnt that once you start the ace-point you should quite often make it. Here we have a lone back blot and remember – attack a blot. The obvious and correct play is 8/2*/1
Key Points to Consider Check Magriels Criteria How strong is your opponents home board Life after death? How is the race? Is your opponent on the bar? How many back checkers does your opponent have? Where is the cube? Gammon risk?
Commentary The race is equal You opponent has the slightly better home board and ten checkers in the zone. None of the basic criteria suggest slotting. You have a good position that can develop naturally Splitting allows a blitz attack and doesnt gain enough in return The simple 6/5 is best – awaiting developments
Commentary The five is obvious – 13/8. Then slot or split. Normally priming a blot is not the obvious plan but here 6/5 threatens to create a five-point prime and if not hit give black a strong position. On the other side of the board once more white has 10 men in the zone and a disjointed position. He would love black to split and give him the chance of a blitz Once you study 13/8, 6/5 the play looks obvious but that doesnt mean its easy to find over the board.
Commentary One could try a Cookesque 13/7, 6/5 but that would be a blunder. 7/1, 6/5 is a better slot However none of the basic criteria suggest slotting here. The race and positions are equal and there is no huge gain from slotting. Time for a quiet waiting play 8/2, 8/7 Not the dreadful 21/14 (duplicating 2s) as played in the game from which this position was taken. White rolled 54 and played 13/4*. Black fanned and had to pass whites double!
Commentary Here everything cries out for the slot 13/7, 13/8 Black has the better home board. If the slotted point is made black will have a very strong position If white hits, black could end up blitzing him because of all the return shots and exposed blots (white may not hit with some of his hitting numbers (e.g. 51) for precisely this reason) White has blitzing potential (this is a recurring theme) The building play 13/8, 10/4 does not meet the demand of the position
Slightly more difficult Correct Play: 15/11, 6/5
Commentary Again all the criteria cry out for a slot: Black needs the 5-pt He is unlikely to make it naturally He is behind in the race He has an anchor Making the 5-pt could lead to a powerful double The correct play is 15/11, 6/5 Any other move is a blunder or worse 13/9, 6/5 is also a big error! 15/11 provides more covers but Im still surprised at the equity difference. Note: The new bot ExtremeGammon prefers 15/11, 8/7 which opens up a whole new debate
… and more difficult again Correct Play: 13/9, 24/23
Commentary This one is slightly surprising as it intuitively looks right to slot with 8/7 However, notice some key points: The race is close There is no real duplication of whites numbers While black builds his prime white will be counter-priming Black does better by splitting 24/23 and attacking whites blots. The plan may backfire and white run a successful blitz but blacks front position (his 5-pt) will protect him to a certain extent. It is not a blunder to play 8/7 but it is an error. This is a difficult problem and many would get it wrong over the board. Note that the do nothing play with the one – 6/5 – is the wrong idea. Black should take action on one side of the board or the other
And really difficult! Correct Play: 23/18, 15/14!!
Commentary Fantastically difficult position from the 2009 World Championship Final! The bots have taught us that when your opponent is on the bar you can take a lot of risks with slotting, especially when you have a five-point home board. Any move other than 23/18, 15/14 is big mistake! Credit to Lars Trabolt for finding the play under the extreme pressure of a WC final. Sadly his play was not rewarded with a win! Key point – when your opponent is on the bar is the time to take risks This position is a graphic demonstration of that principle
Commentary This is an example of turning the game into a one roll proposition Black is crying out for his 5-pt – without it he cant win the game Black must play 14/5. If white doesnt hit he must drop blacks redouble next turn By slotting black makes himself a big favourite. Any other play leaves him with a lot of work to do.
Piano or Forte (2)? Correct Play: 21/16, 11/10 or 21/15
Commentary This one is not so clear The race is closer If black slots and gets hit he could lose a gammon He can get good outfield coverage with either 21/16 or 21/15, 11/10 (note he must ensure he gets hit with whites 55) When good outfield coverage is possible it is often the right play and here black must balance aggression against the gammon risk. Coverage wins and one of the quiet plays is correct.
Commentary At first glance 5/3*, 11/10 looks obvious but White has a four-point board so when black is hit he will lose a lot of gammons The race is relatively close Black is approaching a redouble and should not jeopardise that cube turn His checkers are well distributed anyway and the immediate capture of his 3-pt is not essential to winning the game The quiet play: 5/3*/2 is correct by quite some margin
Commentary Here black is losing and losing badly Whatever he does he will lose a lot of gammons It will take a miracle to save him To do that he will need his 4-pt as soon as possible To do that he must slot it now with the hope of making it next turn 8/4, 24/23 is the only viable play!
Considerations How many checkers off? How strong are the home boards? Strength of outfield coverage? Which point requires slotting? Direct cover or not? (rule of thumb is to have one direct cover before slotting) Where is the cube? How many men on the bar? (never slot against two on the bar)
Commentary The 6-pt is often slotted. Lower points less frequently and the 2-pt and 1-pt are virtually never slotted. The reason is that whenever your opponent enters on the 6-pt he also escapes – that is not true of the lower points. Here there is an urgency to make the 6-pt in order to win the game Black already has two checkers out of play 14/6 is both thematic and correct.
Commentary Just one point difference but now the slot is wrong! Making the point 6 away from the open point is a recurring theme in positions like this 20/14, 13/11 provides excellent coverage without the risk of slotting Whites 3-pt board still ensures that black loses some gammons when he is hit. Its these gammon losses that swing the solution to 20/14, 13/11
Commentary Now the situation is more urgent and white has a weaker home board. Its surprising how weak the opponents home board has to be (normally only two points) before you start taking liberties with slots and trap plays. This (just) swings the answer to 13/5 but that play and 20/14, 13/11 are nearly equal in equity. Note: Once again, ExtremeGammon disagrees and prefers 20/14, 13/11. As Jeremy Bagai says in Classic Backgammon Revisited: The pendulum of style continues to swing throughout the modern era, but the arc gets shorter as progress is made. Maybe, but theres still some interesting material to be found within that arc!
Commentary Another situation where black is closing in on a redouble. Now leaving the points slotted is overkill and when things go wrong they go badly wrong and black can easily lose a gammon. Whites four-point board should set alarm bells ringing Simply best 11/5*/4 Black remains with excellent outfield coverage even if white enters.
Slot or Coverage? The lower the point the less likely (or necessary) the slot. Check for other significant factors Where is the cube?
Commentary These are the ideal conditions for slotting a lower point: White has only a two-point board White has an exposed blot in his home board Black will need his 3-pt to win the game Black cant win with the cube so needs to play aggressively All the criteria point towards the slot being correct The 2 can be played 14/12 or 21/19 as the two plays are equal
Commentary The most famous slotting question in World Championship history. Should Joe Dwek (black) have slotted with this 21 against Lee Genud? Yes he should by playing 9/6. He doesnt have a direct cover but the two blots on the 14- and 15pts give him the equivalent of a direct cover and he must have the 6-pt to win the game. Genud fanned and then Dwek slotted next turn but Genud entered with 65 hitting two blots and won easily from there. Remember – two indirect cover numbers are often approximately equal to one direct cover number