The putter can be swung from one pivot point (a single pendulum) or it can involve multiple pivot points making it a double or even triple pendulum. A single pendulum action allows the player to control the stroke directly from one pivot point. This will ensure a consistent 'Attack Angle', with ball position the only variable as to whether it is struck on the upswing, downswing or the bottom of the arc / 'Low Point'.
With a short putter, the effective pivot point will be positioned somewhere on the upper trunk. If a golfer manipulates the putter with either a wrist break and /or elbow movement then a double or even triple pendulum effect is created through these additional pivot points. In the majority of putting actions this scenario is complicated by lateral motion of pivot points caused by golfers allowing their bodies or legs to move. All of these variables affect the 'Attack Angle' of the putter during the impact zone.
Ideally, we are looking for consistency of the 'Low Point' of the putter along with an 'Attack Angle' of between 0.5 – 1.5 degrees would be recommended.
A negative 'Attack Angle' will create a descending blow (coupled with insufficient static loft on the putter face), will cause the ball to be driven into the ground. You are then at the mercy of the putting green and surface. Attack Angle, Shaft Angle and static loft all effect the launch angle and spin of the golf ball.