When installing alignment shims on the rear of a Mk4, you need to remove the rotor from the stub axle, in order to gain access to the four bolts securing the stub axle. This requires the use of a bearing puller as the bearing is pressed onto the stub axle. Often when pulling the rotor off, the bearing may also become damaged, resulting in a new bearing needing to be purchased.
With this wrench, you can avoid all of the above. The curved ends of the wrench allow you to reach behind the rotor to loosen and tighten the bolts, allowing you to avoid having to separate the rotor from the stub axle. Not only will it reduce the installation time required, it will also save you the expense of needing to purchase new wheel bearings should they become damaged.