2 are provided with apertures for permitting the passage therethrough of wires or cables in practice the blocks forming the panel will be preassembled on a convenient horizontal surface and in practicing the invention suspension cables 6 will be passed through the aligned passages 4 in the blocks from top to bottom of the panel in a preferred arrangement pairs of suspension cables 6 are formed by a single high tensile stainless steel cable looped in two so that the free ends of the cables project from the bottom of the panel to support the bottom of the panel when the latter is lifted and to transfer the weight of the blocks 2 to the suspension cables 6 a bottom support bar 8 is utilized this bar is of inverted channel section and has a number of slots equal in number and spacing to the suspension cables cut into its one side wall and part of the width of its top wall the slots 10 in the top wall allow lateral engagement of the bar with the cables whilst the broader slots 12 in the side wall admit ferrules 14 secured to the ends of the cables 6 the top surfaces 16 of the ferrules form abutments which engage with the lateral.