In Chapter 3, the author examines the role and relevance of mock-ups in the context of emerging digital practice by looking at the example of two built projects by Matter Design/Brandon Clifford and Wes McGee. The chapter seeks to illustrate answers to the question of whether mock-ups are a relic of the past, or something with a continued relevance today in the context of digital computer-generated practices, in which simulation and augmented reality may take the place of empirical experimentation. Somewhat surprisingly, even with advanced tools and technologies, the mock-up is seen in this chapter to be an invaluable tool for calibrating virtual forms in the material world.