IIRC, the front ones slot into the plastic flare from the bottom. i.e. pulling the trim up will unclip them the trip, leaving the clips in the body work.
You cannot put it back on in reverse though, the clips have to go into the trim and then pressed into the body.
When I was putting in the snorkel a firm tug on the plastic trim caused it to unclip from the clips. This does damage the clips though and without new ones, it will not sit flush against the body.
All the above is with the front fender and an old memory. Rear ones and a youthful memory may disagree
