Steven,
yes, both types - the V-shaped ones and the H-shaped ones with 4 barbs - slide out. On the 4-barbed one there is a circular - 2 half moons - depression in the center that fit into a hole in the rail and prevent the clip and therefore the rubber from sliding up or down.
The V-shpaed one have a groove that slides the along rail.
Perhaps a less experienced installer may have used some glue to keep them in place. If that is the case just some solvent and nose pliers to wiggle them loose.