dolly need not be as great as the repeat will not occur until five dollies are stacked versus four dollies in fig2 accordingly the size of protrusion 38 for the embodiment of fig3 or at least the portion of the upper shoulder 42 which becomes the effective distance from one dolly to the next may be smaller than the corresponding shoulders 42 where the protrusion 22 is to be used with the embodiment of fig1 and fig2 turning to fig5 and 7 details of the mounting of the protrusions 22 38 and roller assemblies 18 36 is shown thus as seen in fig5 bolt 48 engages the protrusion structure 22 38 to mount said protrusion 22 38 downwardly from the bottom of the platform 12 32 cushioning material 50 which may be carpet may be used for its friction enhancing abilities as well as its cushioning effect and can be cut out as shown in the pattern of fig6 slots 52 may be cut into the pattern which will accommodate mounting bolts 54 which are shown to mount roller assembly 18 36 to the leg 14 34 as shown in fig7 as can be appreciated from viewing fig5 and 7 the carpet 50.