pocket

• corner pocket rattle and how to avoid it
• pocket "size" and "center"
• point compression

for more information, see Section 3.06 in The Illustrated Principles of Pool and Billiards

corner pocket rattle and how to avoid it

How do I aim to prevent the OB from rattling out of a corner pocket?

This happens when the ball hits the near rail cushion or point with speed before entering the pocket. I have a good demonstration of this effect at NV 3.13. Also, super slow motion clip HSV 3.8 shows why it happens fairly clearly. The cushion imparts sidespin to the ball, changing the rebound angle off the inner wall of the pocket. My Nov '04 - Jan '05 instructional articles also have some good illustrations, descriptions, and online demos of this and other related effects.

pocket "size" and "center"

Does the effective size and aiming point for a pocket vary with approach angle?

Yes. See the diagrams and examples in my Nov'04 - Jan'05 articles. For example, with a corner pocket, at shallow angles to the rail (about 2 degrees from the rail), because the object ball can glance off the rail well in front of the pocket and still go in, the effective "size" of the pocket much larger at that angle.

As shown in Diagram 3 in my Nov'04 article, I measure the "offsets" relative to the geometric center of the pocket at the leading rail edge of the pocket jaws. The offset vs. entry angle plots near the ends of TP 3.5 and 3.6 show how the "target center" varies with entry angle. For a slow shot, the point varies by as much as about 0.6 inches for a corner pocket and about 0.3 inches for a side pocket.

point compression

Is it possible to deform the point (or knuckle) of a pocket enough to force a ball in?

Yes. See:

NV B.28 - Pocket point compression shot

Cushion compression away from the pockets can also be used to help make certain shots. For example, see:

HSV B.20 - rail cushion compression shots