One of the main operations in conceptual 3D design is the rearrangement of single and composite objects. This paper presents a new conceptual 3D design system that affords easy manipulation of composite objects. We discuss several alternative manipulation techniques to separate complex parts off an existing model. Then, we present a new way to move such parts in a 3D scene, as well as an algorithm to place parts at arbitrary locations. Finally, we present and discuss the results of a user study of these manipulation techniques.