Research in the field of Computer Aided Design (CAD) has long focused on reducing the time and effort required of engineers to define three dimensional digital product models. Parametric, feature-based modeling with inter-part associativity allows complex assembly designs to be defined and re-defined while maintaining the vital part-to-part interface relationships. The top-down modeling method which uses assembly level control structures to drive child level geometry has proved valuable in maintaining these interfaces. Creating robust parametric models like these, however, is very time consuming especially since there can be hundreds of features and thousands of mathematical expressions to create. Even if combinations of low-level features, known as User-Defined Features (UDFs), are used, this process still involves inserting individual features into individual components and creating all of the inter-part associativities by hand. This thesis shows that programmatic operations designed for a specific product type can streamline the assembly and component-level design process much further because a single programmatic operation can create an unlimited number of low-level features, modify geometry in multiple components, create new components, establish inter-part expressions, and define inter-part geometry links. Results from user testing show that a set of high-level programmatic operations can offer savings in time and effort of over 90% and can be general enough to support user-specified interface layouts and component cross sections while leaving the majority of the primary design decisions open to the engineer.