is of an enlarged mesh configuration having a pair of lower hooks 83 extending therefrom for engaging into the openings 27 of the last floor unit being placed within the trailer in addition the uppermost portion of the screen includes a support bar 84 having openings 85 in the sides thereof to which anchoring chains 86 may be secured to anchors 87 mounted adjacent the rear portion of the trailer bed and adjacent the uppermost portion of the side walls as is shown in fig5 the rear screen is utilized to securely anchor each of the floor units in relationship with respect to one another during hauling of the palletized cargo the rear screen 82 may be removed and carried by the support rack 70 when not in use in some instances it may only be necessary to provide anti frictional coatings or layers to one or both of the side walls of the floor units and the portion of the trailer side walls intermediate the guides 40 and 42 with such coatings also being provided on the upper surface of the guides 42 as shown in fig5 in the use of the device assuming that comminuted material is to be hauled initially the body of the trailer is loaded the rear door 50 being closed and the removable flooring units being outside of the truck body such as being mounted on the racks as indicated in fig1 the truck is then driven to the destination for the delivery of bulk material where the swinging door.