It is the hidden enemy of the green, the grain of the grass. This issue of Golf Newz will assist you in dealing with this terror of the green. May the greens be kind and the fairways wide. If you are lucky enough to find a putting surface which appears to be perfectly flat, beware of the hidden enemy lying in wait to hijack your golf ball and deliver it far from your intended target. The grain of the grass affects the direction a putted ball takes and, with just a few exceptions, all golf greens have some grain.
Grain is formed by the direction in which the grass is growing, the way the blade tips point.
If the tips lay to the right or left of the line of putt, the ball will roll toward them and you must allow for this. For instance, you have diagnosed that the grain is running to the right of your line. Your course of action therefore must be to aim to the LEFT and allow the ball to follow the blades of grass to the right. When the tips run in the direction of the putt, the ball will roll faster than if they were facing towards the ball. Should those tips be facing the ball, a little more speed will be required to overcome the resistance.