The role of research centres in generating new technology for development is problematic as engineering is no longer an isolated field of human activity. Rather than providing a clear-cut solution, this paper makes the case for the inclusion of this problematic area into research activities and technology-design procedures. In rural development, the classic notion is that of agricultural extension, an organisation that disseminates scientific knowledge and technology. STS provides a different understanding of what extension means. The notion of the lab or studio as the single source of knowledge is an after-the-fact creation, once the network linking labs and farmers has been stabilised (Latour’s point). Based on this alternative understanding, there are two major responses. One focuses at the lower end of the connection, emphasizing the role of users (farmers) and the need to create a participatory learning process. The other response is focused on the top-end, emphasizing collaboration between various partners in the innovation process and the need for system learning. Both responses are highly procedural with the risk of losing sight of the importance of the material, technical and skill factors that have a major effect on who can participate and what type of interactions can be effective. What is needed is a case-by-case approach and the inclusion of basic lessons from STS and anthropological accounts. We illustrate this through the introduction of forage choppers in Uganda. This case shows that there is a need to establish a functional connection between the production of knowledge and technology in research centres and the production of knowledge and technology at the field level.