Product keys are required for installation of Autodesk products and are used to differentiate products that are both sold independently and as part of a product suite. The same version of AutoCAD is in both software packages, but the product key differentiates one package from the other. Make sure you use the correct product key for the Autodesk product and version you are installing. Entering an incorrect product key will result in activation errors. The product keys for Autodesk products are as follows: Product Name.
Many CAD systems modify a surface directly using a normal curve: In Alias there is an intermediate step required for trimming, the creation of a Curve-on-Surface:
Alias Basics: My Alias Workflow