In this article, we apply concepts from symbolic interactionism - a well-established tradition of interpretivist sociology - to investigate the social and political processes involved in a sociotechnical intervention. The intervention was designed to elicit operator involvement in an experimental trial of an advanced manufacturing system at an industrial site in Australia. The interactionist concepts of social worlds, boundary objects and trajectories are used to explore the interrelationships among the theoretical, practical and contextual elements of intervention. We believe that these concepts are flexible intellectual resources that can extend and enrich our understanding of the politics involved in the shaping of work and technology. Such an understanding is necessary if the fields of user participation and sociotechnical design are to move beyond the production of normative discourses and methods into effective interventions in the complex social environments in which technical decisions are made.