System 4 — the gap method
Where the ball arrives after a cushion: gap + carry-over = 4
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The four moves
- Pass the cue between the balls. The line joining the center of your ball to the center of ball 2, extended to both long cushions.
- Count the gap. The number of diamonds between the two points where this line touches the cushions.
- Calculate the carry-over: 4 − gap. It's the only calculation in the method.
- Carry over from the right reference point. Under 0.5: from your ball's actual impact point. From 0.5 up (the usual case): from the diamond above ball 2. Positive: left. Negative: right.
The table, at a glance
| Gap measured | Carry-over (4 − gap) | Counting direction |
|---|---|---|
| 1 diamond | +3 | 3 diamonds to the left |
| 2 diamonds | +2 | 2 diamonds to the left |
| 3 diamonds | +1 | 1 diamond to the left |
| 4 diamonds | 0 | the arrival is the impact point itself |
| 5 diamonds | −1 | 1 diamond to the right |
| 6 diamonds | −2 | 2 diamonds to the right |
| 7 diamonds and beyond | −3 and beyond | the arrival falls off the cushion: no usable reference left |
Two examples
Correcting with side spin
Count the diamonds between the announced arrival and ball 3, on the side that catches up. 1 tip of side spin ≈ 1 diamond if the carry-over was positive, ½ diamond if it was negative (twice as much side spin). If ball 3 falls short, use the opposite spin.
My table
Measure once the gap between the announced arrival and the real arrival on your table, note it here, and correct by that much from then on.
Room / table
Observed correction
Date