Among the numerous ways people make illegal or unauthorized alterations to urban space, of particular interest in recent years have been the creative, local, and often anonymous efforts at informal but functional “improvement” to the built environment where the state or property owners have failed to act – practices I call “do-it-yourself urban design.” Authorities, planners, and community members alike rightfully wonder about the meanings of these actions, and the questions they raise about rights, responsibilities, benefits, and consequences. Building from a

larger qualitative study on DIY urban design across eleven cities, this paper focuses on the motivations, methods, and self-perceptions of the informal placemakers themselves. In particular, it demonstrates the degree to which many members of this group are informed by quite sophisticated knowledge of formal urban theory, planning, and design. I argue that this knowledge enables and inspires their actions, informs their justifications, and produces a complicated degree of self-reflexivity around their place in their communities and the contemporary city more broadly.