This article focuses on management indicators, their emergence, theirs functions and their impact for a public action. It does so through an analysis of the implementation of indicators in three forest management units in Belgium, France and Luxembourg. M. Crozier theory and M. Callon theory are crossed to drawn attention to the manner in which, at the micro-level, indicators are worked out. We argue that these emergent measurements are vectors of a particular ethic of behavior. Our aim is to contribute to the study of indicators in three aspects. First, it offers a more detailed understanding of the double nature of indicators: they constrain action and, at the same time, support actors autonomy. Second, it illustrates the major functions of indicators but also theirs paradoxes: actually, indicators lock and unlock organizations. Third, it brings to light the practical rationality and the ethic of commitment connected to indicators.