To install the backpack mount, unscrew the original mount.
Make sure the rubber inlay is placed accurately in the plastic part. Attach the new mount by using the original screws.
Does the job but switch between different mount is not practicle. For bag-only light.
This mount does the job well but I wanted to be able to switch easyly the like from my bike to my bag/ clothes (when running or if I wear a big bag that mask the light mounted under the saddle). This is not possible because the bike mount (saddle mount for exemple) has to be unscrewed and the bag mount screwed over to switch mounts. An "universal" fixation on the lamp itself that could adapt rapidly multiple different mounts would be mutch practicle.
I bought this mount but I don't think i will ever be using it since I mostly bought the light for biking and I don't want to spend my time unscrewing and screwing back tiny screws all the time. My bad, the installation was explained in the description.