[vj]

A straight left arm is not a requirement using extensor action in putting. Think of it as both structure and rigidity. Extensor action can be applied to the point of both.

Lynn says it best. You just keep pushing until one day BAAMM! It is there and you wonder how you ever played golf without it.

Extensor action gives so much structure (which lends to width) to everything. Don't put it in some strokes, put it in all strokes. Just keep pushing in your practice.