[rchang72]

OK OK OK.. .I dont get it

a zero shift swing is when...

1. the shaft never changes plane
2. the sweetspot never changes plane

The correct answer is sweetspot

Quoting from the book 2-F, "Regardless of where the Clubshaft and Clubhead are joined together, it always feels like they are joined at the Sweet Spot - the longitudinal center of gravity, the line of pull of Centrifugal Force. So there is a 'Clubshaft' plane and a 'Sweet Spot', or 'Swing', Plane. But herein, unless otherwise noted, 'Plane Angle' and 'Plane Line' always refer to the Center of Gravity application."

A zero shift swing is still checked the same way many other instructors teach: the point of the clubshaft nearest the ground points at the plane line, except when the clubshaft is parallel to the ground, then it is parallel to the plane line.