This paper presents an ethnographic study of knowledge reuse in the architecture/engineering/construction industry. Reuse occurs largely through social knowledge networks. Even when reuse from an external repository occurs, a human expert is needed to provide input on what to reuse and contextual information about the designs being reused. This is attributed to the effectiveness of internal knowledge reuse, the reuse of knowledge from one’s personal experiences. Internal knowledge reuse is effective because the designer can find items to reuse, and can recall the context of these items and can therefore understand them. This ethnographic study was used to develop a corporate memory, a rich, detailed repository of knowledge in context. The corporate memory will support finding and understanding. Understanding can be brought about by enabling the designer to explore the item’s context. This helps the designer to manage the tradeoff between productivity and creativity in deciding what to reuse.