The Putting Mirror
Why this drill
Eyes over the ball, shoulders square, stroke moving like a pendulum — putting's setup fundamentals are invisible from inside and obvious in a mirror. Ten minutes of reflected reps build a setup that repeats on greens you've never seen.
Setup
A putting mirror if you own one; a cheap wall mirror laid flat, or a phone filming from face-on, if you don't. Putter, one ball, carpet.
The drill
Set up over the mirror: eyes directly above the ball (or just inside the line), shoulder line matching the aim line. Ten strokes watching nothing but your shoulders — they should rock, not rotate; the moment they open the putt has borrowed a hand flip to save it. Then ten strokes eyes closed, opening only to verify the finish position. The stroke you can repeat blind over a mirror is the one that survives Sunday-morning greens.
One thought to take with you
Eyes over the ball, shoulders do the moving — everything else is furniture.