Abstract: A molded panel for buildings is manufactured in a manner that permits the blocking tab along the upper edge of the panel to be molded in a position that is close to its final desired position. Pressure is applied to the locking tab as it cools, thereby bringing the locking tab into its final position.

Abstract: The present invention relates to a method and apparatus for molding plastic articles. More specifically, the present invention is directed to a staged sequentially separated apparatus for injection molding of plastic panels having a flap or tab molded therewith in a single molding and forming step. The present invention provides, among other things, a method and an apparatus for forming an injection molded part with an undercut, the undercut lying generally in a plane of a major portion of the part, the undercut having an open elongate opening and being positioned between an elongate integrally molded tongue and panel. The apparatus comprising a first mold half with a first mold cavity defining surface, a second mold half with a second mold cavity defining surface, a tongue member carried by the second mold half and projecting into a mold cavity.