How to Mount a Thule Roof Box Mounting a roof box to your luggage rack is a fairly straightforward process. Most of them come with an installation guide as well as a few U-brackets to ensure for a quick installation.
You may need to reposition the holes on your Thule roof box; it takes trial and error. Position the box as close to the center as you can. Then, use the U-brackets to secure the box to the luggage rack. A few quick turns and they should be secured properly.
Do this all the way around the box and it should sit snugly and securely to the luggage rack.