of trays 24 a similar pair of rollers 110 are also provided rollers 108 and 110 serve to limit lateral movement of trays 24 when moving while positioned in the horizontal and vertical positions no appreciable load exists on rollers 108 and 110 rollers 108 rotate only when in contact with casing 12 or tray restraints 111 secured to the casing rollers 110 rotate when in contact with casing 12 or shield 80 shield 80 is a continuous u shaped member extending between upper sprockets 60 61 64 and 65 and lower sprockets 62 63 66 and 67 and serving to separate horizontally positioned moving trays 24 from chains 56 and 57 and vertically positioned moving trays 24 shield 80 thus forms a continuous smooth surface around horizontally positioned trays to ensure freedom from obstruction to movement of cargo reference is made to fig1 16 top and bottom fork assemblies 33 and 35 are installed at first level 18 and first platform level 14 respectively for loading and unloading of cargo assemblies 33 and 35 must be manually set to correct positions before a cargo transfer operation can be initiated for strike down operation hereinafter to be more fully described top fork assembly 33 must be horizontally positioned fig1 and bottom fork assembly 35 30 u00b0 up from horizontal fig1 for strike up operation hereinafter to be more fully described bottom fork assembly 35 must be horizontally positioned and top fork assembly 33 30 u00b0 up from horizontal top fork assembly 33 best shown in fig1 and 12 is provided with a plurality of u shaped members 110 secured in parallel pairs as by welding to rod member 112 rod member 112 is positioned through members 110 and is secured at each end to one of a pair of.