the interior of the pan is filled with a cement mix 20 the basic construction of pan 10 is more fully described in commonly owned u s pat no 4 606 156 to the extent necessary the disclosure of such patent is hereby incorporated by reference in accordance with the present invention the pan is modified to include a peripheral flange arrangement which defines a downwardly opening channel as seen in fig2 sides 16 of the pan extend generally vertically from and are joined to bottom 14 extending outwardly and horizontally from an upper edge 22 of each sidewall 16 is a generally l shaped peripheral flange 24 flange 24 includes a horizontally extending portion 26 and a downwardly extending portion 28 flange 24 in conjunction with sidewall 16 defines a downwardly opening channel 30 a peripheral trim piece 40 is mechanically locked on each flange 24 as seen in fig2 and 3 trim piece 40 is an elongated member or body piece 40 includes an outer curved surface 42 an inner surface 44 and a top surface 46 surface 42 extends from an outer edge 48 of surface 46 downwardly until it joins a lower edge 50 of inner surface 44 as seen in fig2 and 3 surface 44 is stepped in side elevation and includes a lower portion 52 and an inwardly spaced upper portion 54 portion 54 is joined to upper surface 46 at edge 56 a generally l shaped slot 60 opens through inner surface 44 and separates portions 52 and 54 of surface 44 slot 60 includes a first portion or leg 62 which extends in spaced parallel relationship to upper surface 46 slot 60 further includes a second portion or leg 64 which extends downwardly and perpendicular to upper surface 46.