Set two tees just outside the putter head to train centred strike and eliminate off-centre hits.
Set-up: Two tees (or balls) pushed into the green either side of the ball, just wider than the putter head; the putter swings through the gap without touching either.
How to do the gate drill. Two tees either side of the ball, just wider than your clubhead: an off-path stroke clips a tee, a square one goes straight through and starts the ball on your line. A 0:28 film by golf.studio. Film page, chapters and transcript
How wide should I set the tees for the gate drill?
Warren Bennett, Georgia Ball, and Effortless Senior Golf state the tees should be positioned just wider than the putter head or blade. Warren Bennett notes placing them about a ball width outside each side of the clubhead.
Can I practise the putting gate drill indoors?
Yes, Georgia Ball notes that you can push two tees into carpet at home to create a gate for an imaginary hole. Cameron O'Neal and Effortless Senior Golf also suggest using golf balls on a putting mat for this exercise.
Should I use one hand or two hands during this drill?
Effortless Senior Golf recommends practising the stroke through the gate first with your right hand only, then with your left hand only, before making swings using both hands.