Abstract : In general, the dissertation deals with the problem of organizing work. In particular, the issue addressed through the research focused in the practice of directing organizational technical activities. Under this concern, I conducted a field study in a steelworks company located in Santiago, Chile. As part of this endeavour, I approached ethnographically the study of the practice of work in several teams. Each team was made up by engineers and workers, all engaged in carrying out a specialized technical activity. The study was developed during six months, under the framework of a continuous improvement program, in a regular daily daytime shift. Within this context, I focused on interactions (engineers - worker; worker - worker) happening on key workplaces (three control rooms). I also focused in the way engineers conceived plans, from their offices, regarding the work being carried out by their teams. ! In both circumstances, I also studied the way engineers and workers used technologies while performing their tasks. Analysis was based on my field notes complemented with two kinds of video records: interactions between engineers and workers while working, and engineers explaining the way they conceive the work of their team (approximately 30 hours of recordings). Based on activity theoretical and phenomenological approaches, I focused on the interactive construction of meaning through language (speech, prosody, and coordination), gesture (pointing, body position) and the use of space and tools. Analysis conducted suggests the practice of engineers as strongly related with the possibility of continuously establishing a collective activity that results intelligible from the perspective of workers participating from particular workplaces, inhabited by persons and technologies. In order to establish the collective activity, engineers develop a general u! nderstanding of the scene being played from those particular w! orkplace s. A distinctive character of the engineers' practice seems to lie, then, in the possibility of rendering intelligible both: the implications of the planned activity for the work of every participant, and the implications of the action being executed in particular workplace for the layout of the planned activity. In this sense, engineers seem to accomplish the direction of work through the development of a significant understanding of the action pursued at the workplace level and the planned activity level that links action in several workplaces. Within this context, the practice of engineers seems to be closely related to both: presenting the implications of the planned activity at the time and place where work is executed, and representing the implications of the executed work at the time and place where the activity is layout through planning. Finally, research advances in the categorization of several presentational and representational aspects of engineering practi! ce embedded into Information and Communication Technologies used as managerial and operational tools.