Which ones? There's the ones in front of the rear tire which have a screw in the wheelwell side of the trim, and probably a nut on the inside. The trim that wraps around the bumper has quite a few nuts that you can get to from the trunk...depending on the car you'll have to wiggle it out to get it out. The center trim in the rear you can only get off when you pull off the license plate trim piece as one big unit, which takes a few more minutes but its the only way.