A method of installing a panel member on a frame assembly includes the steps of providing a panel member having inner and outer surfaces and providing one or more positioning assemblies on the inner surface of the panel. The positioning assemblies each having an adjustable positioning member adapted to engage a portion of the frame assembly. The method further includes setting the positioning members to determine a registration point for the panel member along the frame assembly. One or more driving assemblies are then provided on the inner surface of the panel, each having a biasing member adapted to engage a portion of the frame assembly to drive the panel member towards the registration point on the frame assembly.