You have two key lines from which you'll make adjustments: your strike-line and your ten-pin line
Different players may have a different "line" but can still use this system, based off their own lines. The strike line will be different from the ten-pin line, too. For simplicity the diagrams here show the two starting lines (in yellow) using the 2nd or 3rd arrows.
To use the 3-6-9 you keep the same target and move your feet more to the left or the right. The lines drawn clearly show how moving more to the right results in the ball hitting pins left of your original line. Similarly, moving left with your feet makes your ball end up further to the right.
Now, all you have to do is decide how far to move your feet. That's simple: you move in blocks of three boards. Each three board move with your feet will cause your ball to hit the next pin down the line.
So, for example, you have the 7 pin left....all you have to do is move 9 boards right and hit your same STRIKE mark. There is one problem with this system. I for one already start one board right of the first dot and throw 2 boards left of the first arrow as my strike target. So for me to make the seven pin on the LEFT lane, I have to start in the middle of the damn ball return!
