Constructing rules for work that foster both health and safety and efficient production entails, in many organisations, the introduction of procedures, tools and techniques implemented by specialists. The purpose of this is to combat the amateur practices and lack of expertise supposedly found not only amongst employees, but also in their managers. This chapter argues that, on the contrary, field managers possess knowledge about working conditions and are actors who are necessarily involved in organising those conditions as well as the work of their teams. In so doing, they protect employees from or expose them to the real and varying circumstances of work. This is the role that needs to be reinforced in order for safety rules to become a real part of work cultures and working practices. However, the forms of power in organisations increasingly limit the recognition of this expertise in the work of managers. The chapter advocates the importance of giving managers power to set situated organisational rules, instead of making these the exclusive prerogative of central management departments.