Loft on the face of a putter can cause a significant directional error of the putter is not soled properly. If a golfer’s putter does not fit them properly, ie either the heel or toe is up at address or during the stroke, then loft on their putter face has to cause a directional error based on physics.
To see this effect dynamically demonstrated watch the video on this subject in this sites Video Library.
By watching the video you will also learn how to minimize this error causing effect.