We study the use of internal cross-docking in Just-in-Time plants. The considered plants consist of a cross-docking zone, a picking zone and assembly lines. The cross-docking zone is used to receive, store (temporarily) and ship pallets. Pallets are then broken into cases and stored in the picking zone which supplies the assembly lines. Cross-docking is used instead of mass storage in order to accelerate the physical flows of pallets. In this paper, we introduce different cross-docking policies (set of rules which specify how to store pallets) commonly used in practice. A cross-docking cost evaluation model is developed in order to compare the cross-docking policies considered in terms of required labour and surface costs.