Ron was recently reading about a modified banking system that I discuss in The Drills section of my website, and wanted to know a little more about how these types of systems are used in the real world. Instead of replying directly to his comment, I decided to write this post. When I first started learning rail aiming systems I was very confused about how the numbering systems worked and where exactly to aim the object ball, but I had no one around to explain them to me. Fear not dear reader! I hope this post will save you a lot of time and reduce the amount of effort it takes for you to learn a system. Keep in mind there are many different systems out there, but regardless of the system you use, there’s going to be a learning curve. It is unrealistic to expect that simply memorizing numbers, calculations, and methods will translate into 100% accurate results.
All systems have certain assumptions built into them, which may include: (1) speed of the cue ball, (2) spin of the cue ball, (3) the degree of follow or draw applied to the cue ball, (4) angle of hit between the cue ball and the object ball, (5) speed of the object ball into the rail, (6) angle of approach of object ball into the rail, (7) etc. No system is perfect, but all systems are designed to give you a very good start along the path to great banking or kicking. You will need to put in many hours developing your own “feel” for these shots. Just be patient and trust the system that you adopt. Keep as many variables constant as possible. Over time you will hone your banking and kicking skills to a razor’s edge. Okay, enough blabbering, let’s get on to the banking system that I use.
Here’s a real world situation. Suppose you are playing 8 ball and your opponent leaves you the shot depicted in Figure 1. You’ve decided that you want to attempt a bank shot to the lower left corner. How do you do it?

Figure 1 - The Situation
Step 1: Let’s call up the modified banking system that I use. I’ll refer to this as the banking “map”. See Figures 2 and 3 below. Figure 2 shows you the numbers that I memorized. Each number corresponds to a location on the opposite rail. Figure 3 shows you how I visualize it in my mind.

Figure 2 - The Banking System (Numbers)

Figure 3 - The Banking System (Visualized)
Step 2: Let’s see where the object ball (“OB”) is located in relation to the banking Map. If you compare the actual location of the object ball in Figure 1 with the Map in Figure 3, you will see that the OB is located on the table surface somewhere between the following two lines: (1) the line connecting the 5th diamond on the bottom rail and its corresponding number {2.25} on the opposite rail, and (2) the line connecting the 6th diamond on the bottom rail and its corresponding number {2.75} on the opposite rail. See Figure 4.

Figure 4 - Locating the OB on the Map
Step 3: Since the OB (the 8 ball) is not sitting directly on one of these lines, but rather is somewhere between lines 1 and 2, you are going to have to interpolate either mathematically or visually to figure out the path the OB will need to take. Don’t worry, this is not difficult. For the super analytical folks out there, you can do a mathematical interpolation between the two rail numbers and figure out the exact rail number you need to aim at. That may be fun for you, but it’s not really necessary. All you really have to do is send the OB on a path that is roughly parallel to both lines 1 and 2. In Figure 5 below, I show you how to visually determine the correct OB path.

Figure 5 - Find the OB path
Now you know the approximate rail number (approximately 2.50) or path the OB needs to travel on. That’s all for the method itself. We are now finished using the banking method! That wasn’t too hard was it?
Looks like we are done, right? Well, not exactly. Remember I mentioned developing a ‘feel’ for shots? Yeah, this is the hard part. You can’t just unscrew your stick at this point and claim victory just because you know the correct OB path. Your opponent is probably going to demand that you actually make the shot. Damn those pesky opponents!
In theory, if the cue ball serendipitously is also on the same path that you calculated for the OB (as in Figure 5), the bank shot is going to be a no brainer. My kitty cat could hit that shot. Well, okay, maybe not, but it should be a VERY simple shot. Just aim straight through the OB and sent it along the path you calculated. I don’t know about you, but in the real world, the cue ball and OB always seem to be conspiring against me. I rarely get a straight in shot when attempting a bank or a kick. That’s why it is important to know the assumptions of your aiming system. Here are the assumptions in my banking system:
(1) The OB must be rolling naturally when it hits the rail (i.e. no side spin and no sliding). In other words, the ball is just rolling naturally straight forward along its path.
(2) The OB was rolling with medium speed (speed affects the angle of reflection when it comes off the rail). “Medium” is of course a qualitative measure: my “medium” may not be the same as your “medium”. This is where practice comes in and you learn what works for you.
That’s it with regard to assumptions. However, to ensure that you comply with the two assumptions above, you may have to do something funky with the cue ball to make the OB comply with these requirements. For instance, check out the Figures below. In Figures 6 and 7, because the OB and cue ball are not conveniently lined up, I’ll have to make some slight adjustments to the cue ball on these shots (as described) in order to hit the bank successfully. The reason adjustments are necessary is because when the cue ball collides with the OB at an angle, the cue ball (due to frictional forces) will impart a small amount of spin to the OB. Remember our method assumption # 1? “The OB must not have any spin.” To prevent collision induced spin, I’ll need to slightly spin the cue ball in the “helping” direction so that the hit between the cue ball and the OB is a “clean” hit with no sliding forces applied. How much spin should I use? Again, this is where practice comes in. In most cases, not much is needed. Maybe a half tip of english.

Figure 6 - Use No English

Figure 7 - Use 1/2 tip Right

Figure 8 - Use 1/2 tip Left
I hope this post helps out. Let me know if I’ve misstated anything or if something is not clear. Thanks for reading, and happy banking!!