The term handling unit (HU) is used to designate a logical warehouse unit that consists of one or several packing materials (load carriers/packaging material), any materials stored on it and any additional HU. Handling unit management includes the management of HUs in the WMS. Typical load carriers for a HU are e.g. pallets, wire-mesh pallets, containers, shelf boards, and cardboard boxes. Nesting of HUs allows for a clear hierarchy to be created. (In order to e.g. map the structure of a tray or of the package, it is important to know the HU’s spatial positioning as this must also be accounted for.) Each HU is assigned a unique number for identification and management in the WMS. This identification allows for handling units to be traced so they can be used for storage, transport, or dispatch.