Plumb-bobbing is all about determining where vertical is so that you can see how much break a putt will have. Plumb-bobbing shows the general slope of the green from your ball to the hole. (And plumb-bobbing is one reason — along with old-fashioned polyester pants and electric carts — that nongolfers laugh at golfers.)
To determine your dominant eye, make a circle with the thumb and index finger of your right hand a couple of inches in front of your face.
You need to know which eye is your dominant eye because you close the other eye when plumb-bobbing.
Look through the circle at a distant object.
Close your right eye.
If the object is still in the circle, your left eye is dominant. If, of course, you can still see the object in the circle with your left eye closed, your right eye is dominant.
Stand as close to the ball as possible and, keeping your dominant eye open, hold your putter in front of your face and perpendicular to the ground so that the shaft appears to run through the ball.
Now look to see where the hole is in relation to the shaft. If the hole appears to the right of the club, the ball will break from the shaft to the hole — from left to right. If the hole is on the left, the opposite will be true.