A method of assembling a z-bar extension member to a z-bar that negates the need for trimming the z-bar. The apparatus includes an exterior z-bar member having an exterior barrel portion and an interior z-bar member having an interior barrel portion. The interior barrel portion is slidably or snappingly engaged within the exterior barrel portion. Mating structures may be included on the cooperating components to maintain a positional relationship therebetween during assembly. A guard assembly that mounts to the edge of a door or on the end of a door expander to cover the gap between the z-bar and the casing is also disclosed that may be used in conjunction with or as an alternative to the z-bar extension member.