The paper is devoted to a practical case taking place in the Rotterdam harbour. A group of stevedoring companies founded a pool of dockers to be able to share human resources. In this way they cover their strongly fluctuating workload. A system to control the pool is developed. On the one hand this system divides the liabilities of the pool among the stevedores and on the other hand it rules the priorities of assignment of human resources. The history leading to the development of this system is discussed, the system itself is sketched and finally some experiences with the system are given. In an appendix some mathematical aspects of the assignment rules are treated.