Push-Back System
The system operates very simply:

Each level of racking includes two or three parallel trolleys at different heights. The fork-lift places the first pallet on the highest set of parallel trolleys. When loading the second pallet, the fork-lift pushes the first one along until it reaches the next set of trolleys, and deposits the pallet on these. If the installation has been designed to store four pallets, the operation is repeated with the third pallet and the last one is rested directly on the rolling rails, rather than on the trolleys.
When unloading pallets, the modus operandi is reversed, in such a way that when the first pallet is removed, the others move forward one place towards the aisle.

Both the rolling rails and the trolleys rest on the racking beams. These are assembled with the necessary slope so that the trolleys will move correctly. The levels are built to house one or two storage channels. In addition to the rolling elements, each trolley also has a safety bolt that prevents it from moving if the pallet has not been placed correctly. There are centralizers on both sides of each channel to centre the pallet. These help to place it in the correct position with the stops of the front beam. The fact that the rail is I shaped means that the rolling elements slot over both sides of the central beam, thus ensuring correct movement and preventing any possibility of derailment. The front beams have support and fixing elements, as well as stops and holes, allowing a small piece of the available trolley to stick out. This is particularly important for high levels.  The system can be adapted to store two, three or four pallets deep. Once the model and measurements of the pallets have been analyzed, together with the available space and the type of forklift to be used, the number of pallets can be specified. The construction system is similar in all cases. The only things that change are the number and measurements of the trolleys and rails.

Another variation of the trolley system is the system made up of roller channels. This works in a similar way to the trolley system, but rollers take the place of rails and trolleys. The construction system is the same as that used for the live storage system, but the pallets are put in and taken out from the same side. With this system, the narrow side of the pallets is the side that is handled, so that the stringers of the pallets rest perpendicularly on the rollers, thus facilitating movement. Given that the channels slope slightly, when the first pallet is removed, the rest move forward one position. In order to choose the most suitable system, an analysis should be made of each customer's needs regarding capacity, number of SKU's and operating system.