The 2.25 Inch Rule
When playing position, the smaller increments you can divide the table into, the more precision your game will acquire. A convenient measurement for learning this type of thinking is to divide the table into 2.25” increments, which is the diameter of the balls. You can then use the balls to accurately set up practice routines that teach you position play and the effects of small differences in the location of the balls. You will quickly discover that 2.25” has a significant impact on the cue balls path.

Practicing the 2.25 Inch Rule
1-ball For example, try the practice drill below. Place two balls directly opposite the second diamond, then remove the ball closest to the rail. Next, place the cue ball in the exact center of the table. This will give you the 40-degree cut shot on the 1-ball as shown. Use a full tip of draw (no english) and a medium hard stroke. The diagram shows where the cue ball struck the lower side rail when I shot it several times. (Note: your stroke and playing conditions could lead to a slightly different result on all of the shots in this routine.) Shoot this and the following shot several times. And be sure to mark the contact point on the second rail after each shot with a coin.

3-ball  The 3-ball was played the same as the preceding two shots. Notice how much wider the return angle was for the shot on the 3-ball versus the 2-ball.

Your Results
Now look at the position of the coins. You will discover that the cue ball’s contact point with the second rail will vary much more as the object ball is moved further from the rail. The dispersion pattern for theshot on the 1-ball will be very tight while that for the 3-ball will be much wider as small differences in suing, pocketing, and speed are magnified.

Drill #2, Etc.
After completing this drill, you can add to you knowledge of small increments by moving the cue ball 2.25 inches in any of four directions from its present location (left or right, up or down).

I figured Roger would make the 9-ball even with the cue ball frozen to the rail, as the shot was not too difficult if played correctly. But when Roger started fiddling with his bridge I began to fear the worst. Roger wound up using the closed bridge you normally use for shots on the bed of the table. With his cue now elevated at about a 15-degree angle, his chances of making the shot had probably dropped from 95% to 50% or less. Sure enough, Roger missed the shot badly, handing the set to over his opponent.

I asked him the next day why he used the closed bridge and he said it was because he feared miscuing. I then had him play several frozen to the rail shots with a nearly level cue (elevation of 1-2 degrees) and he pocketed the ball cleanly nearly every time. 

A Very Common Error
The fear of a miscue on rail shots, which leads to the use of an elevated bridge on these shots, is one of the most common mistakes amateurs make. The problem with the elevated bridge on rail shots is that the cure (for miscuing) is worse than the ill. 

The big problem with the elevated bridge is that the tiniest error in your stroke is highly magnified due to the downward hit on the cue ball. A couple of millimeters of unwanted sidespin will cause the cue ball to curve significantly offline. This leads to missed shots in which the object ball fails to even scare the pocket.

Solving The Problem
If you also suffer from the believe that you will miscue on frozen rail shots, I suggest you try the following exercises. 

Exercise #1
Place a stripe ball on the table with the stripe level as shown. Use an open bridge and place your tip on the vertical axis with half of the tip above the stripe and half below. Shoot the ball towards the middle of the far end rail with just enough speed so that the stripe ball returns the middle diamond under your cue..

This will teach you the maximum speed with which you would almost ever want to use with a rail shot. Cueing in this position also duplicates the place you would be hitting the cue ball if it were on the rail!! I’ll bet you didn’t miscue, did you?

Exercise #2
Now place the stripe ball up against the end rail as shown below. Use an openhanded rail bridge and keep your cue level, just as you did when playing the shot in the previous exercise. Once again, you want to contact the cue ball with half of the tip above the stripe, and half below. Use enough force to send the cue ball to the end rail and back to the foot sot If your mechanics are sound, you should have no problem executing this shot without a miscue.

Exercise #3
For those of you who aren’t convinced that an elevated bridge on the rail is a big mistake, I suggest you try this drill. Place any ball in the same position as in the previous drill. Now aim at the opposite middle diamond. The goal is to hit the ball and have it return to its original location. I think you’ll be amazed at how far off line the ball is on 90%+ of your attempts.