fig6 and 7 illustrate a practical embodiment of an indexing mechanism capable of use in the present invention that is mechanically restrained by means of a common torque tube or shaft 6 with indexing gears 7 that engage through the notches 2 which form a rack in the sides of the tray 0056 fig8 and 9 show another preferred embodiment utilising a different form of indexing gear and shape of notch to that which is described in detail with reference to fig1 to 7 fig8 and 9 show the restraining mechanisms being formed by a sprocket wheel or gear 7 having circular tapered engagement sprocket teeth 8 which engage in circular holes 9 in the engagement rack 51 formed at the ends of the tray 10 u2032 the circular tapered teeth 8 provide not only alignment entry and exit in the vertical plane but also in the horizontal plane fig9 is a partial section view viewed from the underside of the tray 10 u2033 in another simple embodiment of the invention fig1 a vacuum formed tray includes cells 11 shaped with chamfered corners 50 that allow sufficient space in an upper flange zone between the corners of four adjacent cells to provide a sprocket engaging aperture 12 fig1 shows a tray with circular sprocket engagement apertures 12 and fig1 shows a tray with square or rectangular sprocket engaging apertures 13 fig1 and 13 show a section through trays of the type shown in fig1 and 11 essentially between the cells of adjacent cell rows fig1 being a section view at 90 u00b0 to the section of fig1 the arrangement utilises multiple sprocket or gear wheels 7 each engaging with a respective row of apertures 12 or 13 0058 fig1 shows another preferred embodiment as viewed from the underside.