This tool is used to measure the end float on aircooled vw engines. You mount it to the upper engine mounting stud using the supplied bolt and nut, Pull the flywheel out, wind in the screw so it touches, push the flywheel in and take the measurement between the flywheel and screw with feeler gauges. using this measurement you can work out the shims needed to set the correct end float We also sell a flywheel locking tool and flywheel seal in the Wolfsburg Restos ebay shop.