Aids in the alignment when installing new golf grips, but in particular putter grips. Install on the shaft and slide up close to the existing grip. Carefully align the tool to the golf club head using the sight lines on the tool. Remove the existing grip and install the new one. There is a vertical line sight line to line up with the leading edge of the club, and horizontal sight lines to line up with aiming lines etc on the putter head itself. If you cant put a grip on straight with this tool, you need an optician. You need at least 60% infill to obtain a nice firm grip on the club without it slipping. The more infill you use, the tighter it will grip the shaft. But the harder it will be to get on and off. So the decision is yours. This MUST be printed in TPU. You will not be able to get it on and off the club shaft with any other material.