heating wire or cable fig9 a shows the heating element 970 as having a generally vertical rectangular cross section fig9 b shows two of the boards 900 interlocked adjacent to each other fig1 a is a cross sectional view of a board 1000 having a top cap coat 1001 and a lower cap coat 1002 a male side of the board 1014 includes an upwardly projecting bump 1016 and a lower pivot bump 1017 a female side 1020 of the board includes a projecting bump 1022 that can snap over and interlock with the projecting bump 1016 a flexible tap 1032 which can help hold the boards together in alignment and accommodate for expansion of the boards and a water drain channel 1024 further the female end has an open area to the inside of the flexible tab 1032 which can be sized and dimensioned to receive a heating wire or cable fig1 a shows the heating element 1070 as having a generally vertical rectangular cross section fig1 b shows two of the boards 1000 interlocked adjacent to each other in this embodiment the aperture on the female end is shaped more vertically so that the heating element can be oriented more vertically fig1 a is a cross sectional view of a board 1100 having a top cap coat 1101 and a lower cap coat 1102 a male side of the board 1114 includes an upwardly projecting bump 1116 and a lower pivot bump 1117 a female side 1120 of the board includes a projecting bump 1122 that can.