the assembly comprises first and second tracks of extruded polyvinyl chloride plastic which , when interfaced , become a hinged clamp . when snapped or clamped together , the tracks tighten and securely clamp fabrics of varying weights . by providing relatively elongated tracks , the installation of the fabric is greatly facilitated in that extended marginal edges of the fabric can be clamped in a single clamping motion . there is no need for a special tool requiring successive stuffing of the fabric into a biased slot and the labor and time involved therewith .