Abstract: The present invention relates to an arrangement for attaching a plastic panel to an automotive body metal substructure enabling controlled distortion free thermal expansion and contraction of the plastic panel relative to a metal substructure. The attaching arrangement comprises a plastic adjustable mounting block sized for initial insertion in an associated wide slot portion of a keyhole-shaped expansion and contraction slot. The block has a central abutment portion depending from an upper plate portion including lateral extending wings providing with the plate opposed grooves adapted to slidably engage a narrow trailing slot portion of the keyhole-shaped slot upon the blocks subsequent longitudinal rearward movement.