Hit the upper clip in the rear pillar trim (A) with your hand. The clip is under the point (B) where the triangle mark (C) on the edge of the trim indicates. Hitting the clip breaks the projections (D) on the pin (E) and pushes it into the grommet (F) and against the body (G). The grommet becomes narrow.

NOTE: The clip must be replaced with a new when the front pillar trim is reinstalled.