This device was designed to allow golfer to keep head motionless but can actually be used to judge the amount of movement.
I have used the following simple method to trial it on the range:-
I arrange a golf shaft to hover 6-8 inches above the ball so that it obscures my view of the ball at address. ( place an upturned range ball bucket 3 feet infront of your address position and run an old shaft through the holes so that the grip end is suspended above your line of sight to the ball) Backswing head movement means that I see the ball completely( to the right of the shaft). I don't mind a little motion that direction BUT If i make sure i never see the ball appear to the left of the shaft then my head has not slipped forward of its address position.( this is what kills me sometimes)
If you follow a stationary head then just make sure that your clubshaft always "eclipses" the real ball ... a good way to encourage swinging through impact too!
If you follow the "search for the pefect swing" findings of the impact head location ( driver) being 2-3 inches down and right of address position then this is the equivalent of seeing the whole ball to the right of the shaft at impact.
I DO NOT WANT THE THREAD TO DISINTEGRATE INTO A DEBATE OF WHICH IS CORRECT ... please....please... just see what you think about this means of self-monitoring head movement.
NOW you can judge what your head (at least your eyes) are doing during the swing.
Here is the little device i made to help completely hide the real ball... best use for a pinnacle golf rock i can find!!
PS i am not the inventor and have no product to sell!
PPS . I posted a very similar thread on another site and had little/ no response. Please positive or negative feedback doesn't matter ... see what you think. Thanks