Many digital approaches to 3D object modeling and deformation are based on sketch and sculpt metaphors due to the widespread use of traditional media in conceptual design. In this research we explore the actual use of physical materials like clay in digital modeling. Users physically sculpt clay proxies of digital models, where the clay is used as a "3D shape cursor" to control the shape of a region of the model. The region can take on the absolute shape of the clay, be deformed relative to a prior clay shape or be virtually stamped back into the clay for subsequent uses. We use a motion capture system as an interface for users to interact with physical proxies of models and a 3D scanner to capture the changing clay surfaces. The differences between successive point-cloud scans are used to define and edit corresponding regions on the surface of the model.