Abstract. Engineering design is a knowledge intensive activity. Design is characterized as comprising a number of phases from requirements to detailed specification. Transitions between the design phases stem from decisionmaking processes supported both by generally available domain and design knowledge and from unique and original knowledge worth of recording for future reuse. The Clockwork project addresses the problems of representing, sharing and reusing knowledge in a collaborative design engineering environment. The Clockwork knowledge management methodology is supported by a webbased toolkit that allows designers to share, formally and informally annotate and reuse engineering models. Reuse is supported through the semantic search of engineering models and of the design rationale by which the engineering models were developed. The approach has been successfully deployed in two industrial organisations.