His belief led to the development of procedures for collective bargaining and contracts between labor and management that remain in use today. In practice, AFL unions were important in industrial cities, where they formed a central labor office to coordinate the actions of different AFL unions. Issues of wages and hours were the usual causes of strikes, but many strikes were assertions of jurisdiction, so that the plumbers, for example, used strikes to ensure that all major construction projects in the city used union plumbers. In this goal they were ideally supported by all the other construction unions in the AFL fold.