Here's a student learning how to control the face to path relationship with a little visual feedback. The overwhelming majority of putter start line comes from club face position at impact. This student was able to understand why the ball had a tendency to start left after seeing the face closed compared to the image on the Visio Putting Matt.

Image one - end of the session - club at impact
Image two - beginning of the session - club at impact
Video one - beginning of the session
Video two - end of the session