Plumb-bobbing is an effective way of measuring the slope of the green.
Greens are full of deceptive slopes and undulations. The vertical line created by hanging the putter in front of you gives a useful pointer for the subtle slopes around you on the green. On hilly courses it helps you keep an idea of the true horizontal, as the humps and hollows can be deceptive.
ASSESS THE BREAK
You can also plumb-bob to asses the amount of break in your putt. Sometimes a putt can look straight but be affected by slopes that you can't see with the naked eye. Plumb-bobbing helps you to adjust your putt accordingly.
To plumb-bob correctly, you need to use your master eye. To find which one, with both eyes open, hold your forefinger at arms length and line it up with a point in the background. Then look with each eye separately, closing the other as you do so. The eye which shows your finger nearest the point in the background is your master eye.
Stand a few paces behind your ball, on a direct line with the hole. Hold your putter with one hand... between the thumb and tips of the fingers near the bottom of the grip. Hold it loosely at arms length opposite your master eye with the toe or heel facing directly away from you.
Line up the center of your ball with the lower part of the shaft. Let your master eye come up the shaft until it is level with the hole. If there is a slope, the hole will be to the right or left of the shaft. Adjust your borrow accordingly. If the slope is obvious, plumb-bob to confirm exactly how much.
CHECK OUT THE HOLE
Sometimes the last few rolls before the ball reaches the hole can have a marked effect on your putt. After plumb-bobbing, check how the hole is cut.
Greenskeepers often pull up the hole cutter at an angle. This means that one side of the hole is higher than the other.
For instance, if plumb-bobbing has shown you have a left-to-right putt, and the hole is cut higher to the right you must adjust the line... the putt is now almost straight.
Lesson 1: By PoGo
Lesson 2: Sloping putts
Lesson 3: Putting on two tiers
Lesson 5: Judging the grain
DRILLS and GAMES