Based on extensive empirical observation of design activities that might be supported by a knowledge repository, we report conclusions from three case studies. Seeking to improve research infrastructure necessary to cultivate a "science of design" within human-computer interaction, we focus on identifying essential activities that help proceduralize the key requirements of knowledge management within a software development effort. From related literature, we selected five focus points for our analyses, which in turn, guided development of our repository in terms of how design knowledge is used, reused, and harvested through system tools. The case studies successively validate potential activities, while exposing breakdowns in process or practice that show promise of being resolved with additional tool features highlighted in other cases. Emerging largely from our case studies, we present general guidelines and tradeoffs for developing a design knowledge repository, as well as directions for further empirical study.