1. A metrology model building tool comprising computer-readable instructions stored on a non-transitory, computer-readable medium, the computer-readable instructions comprising: code for causing a first computer to receive an indication of a selection of a first re-useable, parametric model by a first user to describe at least a portion of a first semiconductor device, wherein the first re-useable, parametic model includes multiple geometric elements and is fully defined by a first set of independent parameter values; and code for causing the first computer to receive an indication of a selection of the first set of independent parameter values.