This application discloses a computing system implementing tools and mechanisms to generate a composite solid model for a set of parts and utilize the composite solid model during the layout process. The tools and mechanisms can identify multiple parts available for inclusion in a circuit design, combine component models corresponding to the multiple parts into a composite solid model, and place the composite solid model in the layout representation of the circuit design. The composite solid model can have physical dimensions that overlap with physical dimensions of the component models corresponding to the multiple parts.