Cross-docking is a logistics strategy used to accelerate the flows and to reduce inventory levels. In this paper, we consider the case of cross-docking centers applied in JIT manufacturing systems. We make a comparison between different cross-docking positioning policies: per supplier, per time slot, per mixed small/big time slots and per mixed supplier/time slot. We intend to shed light on the impact of different characteristics of the system like the supplier arrival frequency and the capacity of cross-docks on the performance of each cross-docking policy. The case study of Faurecia, an automotive parts suppliers, is used to consolidate the insights of our paper. We find that it is better to use the mixed cross-docking because it permits to minimize the used surface and to facilitate the realized movements.