This simple aid is a big hit in my clinics. It is composed of two golf balls, cut down and fused together. Checkerballs provides great feedback in the effort to establish a square putter face at impact. If your putter head is square at impact, the ball will roll with the stripe going end over end. If your putter face is open or closed at impact, the ball will wobble like an egg. You will be able to work on your stroke at home with this aid. Since you are not putting to a target, you can focus totally on stroke improvements. You will find this training aid is hard to quit using—it is addictive!