means of welding gluing or stitching the sheets may be fixed together along lines thereby defining the compartment as a continuous channel or at individual points the variant shown in fig3 d consists of a film or extruded material 47 which has a textured or embossed surface and which is stretched over the outside face of the cushion 11 the function of the textured or embossed surface is to slow the passage of rain water over the surface of the cushion and clearly many textures and embossed patterns could perform this function the preferred material for all the variants in fig3 a to 3 d is etfe due to its long life but clearly other films woven or extruded materials are possible the exemplary embodiment shown in fig4 to 7 consists of a frame 55 holding an etfe foil cushion 51 which is inflated by air via a plenum 56 and which incorporates a rain suppressor 57 as is the case in the previous embodiment and its variants in this case however the rain suppressor 57 consists of a further sheet 52 of an extruded material which is partially fixed by welding gluing or stitching to the uppermost etfe sheet 12 to form a fluid tight compartment 53 between the two sheets 12 52 the fluid tight compartment 53 is filled via a hose 59 with a distilled water when it rains or when the cushion 51 is required to form.