Abstract: An apparatus for increasing the rigidity of an elongate plastic member having a groove formed in an exterior surface thereof is an elongate metal reinforcing member, preferably having a generally T-shaped cross section, the member being adapted for placement into the groove so that the member fits snugly into the groove. An improved elongate plastic member has a reinforcing member formed, preferably by roll forming, into a rigid structure, preferably having a substantially T-shaped cross-section when viewed end-on. The insert fits tightly within a groove in the plastic portion of the improved elongate plastic member. An elongate plastic member is provided structural strength by forming in the plastic member a groove adapted so that a reinforcing member will fit tightly within the groove and then placing a reinforcing member into the groove.