This is a blueprint for assembler items that take 3 input items. The middle three belts pull items from the Logistics Station and the outer two belts return the items. The assemblers are also staggered for ease of putting these next to each-other which allows the assemblers to use one belt for returns when you line them next to each other (final screenshot shows this in action). The only problem is you must put down the sorters to put the items onto the belt for the second placed blueprint.