Two Most Important Position Tools

Vital Pool and Billiards Position Tool #2: Understand that in this diagram, the cue ball is striking the 12-ball so that, if coming into the hit from any angle off perfectly straight (straight along the blue line as indicated), it will roll along a tangent line, which is perpendicular to the line of centers if the spin and speed were such that the cue ball would have stopped if the shot line was along the blue aim line.

In other words, taking a stop shot stroke into the 12-ball at an angle will result in a 90-degree angled position line for the cue ball after object ball impact.