a reinforcing side bar 16 attached on each side 13 at each side 39 s approximate vertical midpoint and extending horizontally along the frame 39 s longitudinal axis end to end 14 as may be best understood from fig3 and 4 a platform 20 with top 21 and bottom 22 faces is fitted onto the top 11 of the chassis 10 the platform 20 is generally flat and also has two sides 24 and two ends 23 the platform 39 s top face 21 has three rows 25 of roller bars 26 one row 25 is positioned near to each platform end 23 and the third row 25 is positioned across the middle of the platform 20 the rows 25 are parallel to each other and are positioned so that each row 25 is oriented perpendicularly to the platform 39 s longitudinal axis and each individual roller bar 26 is oriented parallel to the platform 39 s longitudinal axis a rod 65 is positioned across the platform 39 s top face 21 in line with the longitudinal axis of the platform 20 the rod 39 s ends 66 are inserted through the top end crossbars 19 of the chassis frame 10 the rod 39 s ends 66 terminate in turning handles 67 the rod 65 has two machined knurled gears 68 formed concentrically about its surface circumference the gears 68 are positioned along the rod 65 so that each gear 68 is positioned between the roller bar middle row 25 and one.