is bolted to outer side members 32 34 stationary frame 14 further includes front vertical members 38 40 extending upwardly from the ends of front end member 22 rear vertical members 42 44 extending upwardly from the ends of rear end member 24 and a pair of intermediate vertical members 46 48 as shown in fig5 short cross members 50 52 are mounted to the lower ends of intermediate vertical members 46 48 respectively extending inwardly therefrom the lower surface of each of cross members 50 52 rests on and is supported by the upper surface of outer side members 32 34 respectively and the inner ends of cross members 50 52 are mounted to inner side members 26 28 through bolts 54 56 respectively wheels 58 rotatable about a vertical axis are mounted to each of vertical members 38 40 42 44 46 and 48 referring to fig2 and 4 leg assemblies 18 are mounted to movable frame 16 each leg assembly includes a telescoping extendible and retractable lower portion 59 movable frame 16 further includes a pair of end members 60 62 and a pair of spaced side members 64 66 extending between and interconnected at their ends with the ends of end members 60 62 a central frame member 68 extends between and is interconnected with the mid point of each of end members 60 62 a series of cross members 70 extend between and interconnect central frame member 68 with side frame member 66 similarly a series of cross members 72 extend between and interconnect central frame member 68 with side frame member 64 u shaped track members 74 are mounted to the upper surface of each of cross members 70 and.