Multi-level tray sorting systems consist of several stacked sorting floors, in which sawn timber is sorted – classified by dimension and quality mixed or unmixed – is sorted into the respective tray by opening the pertaining box hatch. The transport of wood to a specific level is made via an inclined drag conveyor (upward or downward).
The maximum capacity of a level is ideally big enough to accommodate the amount of timber that is required to form a complete package. Single-board layer trays, where individual pieces of timber are kept in a row one after another, need a correspondingly large space due to the necessary length of each layer.