In this article, we analyze conversations in consulting meetings where people work across disciplines to design things. We focus on interactional processes through which people disrupt and attempt to change representational technologies for scientific and technical classification. Our case material is drawn from ethnographic and cognitive studies of work in field entomology and architectural design. In both cases, we find common structures of interaction when people work across disciplines. These include selective use of talk, embodied action, and inscription to animate representational states that make up design alternatives. Participants from different disciplines animate situations in strikingly different ways, but these differences can either go unremarked or be put into coordinated use without explicit, shared understandings. Differences become remarkable either when a design proposal runs counter to deeply held disciplinary objectives or threatens to destabilize a wider network of representational technologies. These kinds of disruptions, and their consequences for representational infrastructure, are a central problem for research on distributed cognition.