Abstract: An extruded plastic channel receives the plastic film and a plastic locking strip is then engaged within the channel and under opposed overhanging beads on each side of the channel to clamp the film in position. One of the beads on the channel extends inwardly substantially parallel to the base of the channel and the other bead extends upwardly and inwardly and is connected by a relatively thin web, to the side wall of the channel. This last mentioned bead flexes outwardly as the locking strip is snap engaged within the channel. A flexible extension is formed on the underside of the first bead and extends downwardly and towards the side wall from which this bead extends. This presses against the bead of the locking strip when in place and maintains the locking strip firmly in position regardless of the thickness of film used thus enabling the device to be used effectively with films of different thicknesses.

Abstract: An extruded plastic channel receives the plastic film and a plastic locking strip is then engaged within the channel and under opposed overhanging beads on each side of the channel to clamp the film in position. One of the beads on the channel extends downwardly towards the base of the channel and an expansion bead or member extends upwardly from the base of the channel outboard of the outwardly extending bead which can flex sideways under pressure to compensate for different thicknesses of film. One embodiment includes a membrane connection between the downwardly extending bead and the expansion bead so that when the locking strip is snap engaged into the channel, the sideways displacement of the downwardly extending bead also moves the expansion bead outwardly to facilitate the engagement of the locking strip within the channel.