In pool, or any other billiards sport, side spin has a dramatic importance to the game because of the way it affects the trajectory of the cue ball off the rail. English allows many more options than what is normally available with top, center, or bottom spin since it lets you take different paths to get position on your next shot. Granted there are complications to using English such as throw and swerve, but these extra variables are well worth the risk depending on the shot.
So when the cue ball hits the rail with left spin, the cue ball will turn left off the rail, and when it has right spin it will go right. This can help increase or decrease the angle of the cue ball if you need precise position or want to avoid scratching in the side pocket off of a rail.
Effect of english on the rail
In order to get you used to putting English on the cue ball here’s a drill that will increase your skills and understanding of how English works. Set up 3 balls on the rail from the side pocket on the long rail about a half ball apart from each other. Then place the cue ball on the second diamond. From here aim straight across the rail at the opposite second diamond and try to use English to hit the balls on the rail in order.
You should notice a few things after trying out this drill for a couple minutes. The farther to the edge of the cue ball you get the more side spin gets on the cue ball. And the harder you hit the cue ball the less it catches on the rail which means using a consistent speed is important if you want to hit the balls on the rail on a regular basis.
Hitting the cue ball accurately is a big factor for consistently accomplishing this drill. There may be times where the cue ball reacts off the rail unexpectedly which can be confusing if you don’t know what’s going on. In some cases it might be the speed you hit the cue ball, but in a lot of cases if the cue ball reacts unexpectedly the you hit didn’t hit it where you were trying to hit it. If this happens to you, come up with a hypothesis for why you missed and adjust on the next shot.