A thermoplastic article can be mounted to a support structure by a fastener. The article includes a molded body having a length. The molded body also has an attachment surface configured to face the support structure and a show surface opposite the attachment surface. The molded body defines an interior channel separating the attachment surface and the show surface. The article also includes a attachment boss coupled to and extending from the attachment surface for receiving the fastener to mount the article to the support structure. The attachment boss extends through the attachment surface and into the interior channel of the molded body for reinforcing the attachment boss at the attachment surface.