a segregable material can be used where the user can break off portions of the end cap 21 61 or 71 to achieve a fit from the generally planar second surface 31 a number of structures rise up located near the four corners of universal end cap 21 a series of four projections 33 extend toward the viewer with respect to fig2 the projections 33 will typically fit into a channel 39 s corners at the adjacent junction between its walls a four walled square channel will have four corners and will thus utilize all four projections a u201c u u201d shaped channel will typically utilize two of the projections in the lower two corners between a base wall and side walls to make the four projections easier to fit within the u201c u u201d shaped channel the distal most portion with respect to the second surface 31 may have a slanted end surface typically as an end cut slanted down and away from the center of the universal end cap 21 or from a common plane in order to facilitate the insertion of the universal end cap 21 into a u201c u u201d shaped channel not shown even the two upper projections 33 are expected to give some lateral stability with respect to the side walls of a channel having an open upper extent the rear side of universal end cap 21 shown in fig2 also has bilateral symmetry for a given size of u201c u u201d shaped channel two of the projections 33 rest at the.