Let the putter face open and release on an arc
A good putting stroke is not perfectly straight-back-straight-through; the blade opens and closes slightly through the stroke. For a right-hander, the face rotates slightly open as it swings back and releases the other way through the ball, described as the correct open and release of the blade. Shorter strokes produce less rotation, while longer strokes arc more.
Channel: Mark Immelman
Watch official source at 2:59Why this context matters
Explained while demonstrating the Putter Master putting training aid.