Also, pallet racking retainer plates may be provided on the front of the rack of
this invention to prevent the second pallet added to the rack, which is supposed to rest on the lower cart, from accidentally engaging the lower cart to drive it rearwardly and instead rest on the rails rather than the lower cart. This, of course, would prevent a third pallet from being placed on the rails, so that undesirable happening is prevented by the pallet retainer plates.