This article addresses the generation and use of manufacturability constraints for design under hybrid additive/subtractive processes. A method for discovering the natural constraints inherent in both additive and subtractive processes is developed; once identified, these guidelines can be converted into mathematical manufacturability constraints to be used in the formulation of design problems. This ability may prove to be useful by enhancing the practicality of designs under realistic hybrid manufacturing conditions, and supporting better integration of classic design-for-manufacturability principles with design and solution methods. A trade-off between design manufacturability and elegance has been noted by many scholars. It is posited that using realistic manufacturing conditions to drive design generation may help manage this trade-off more effectively, focusing exploration efforts on designs that satisfy more comprehensive manufacturability considerations. While this study focuses on two-step AM-SM hybrid processes, the technique extends to other processes, including single-process fabrication. Two case studies are presented here to demonstrate the new constraint generation concept, including formulation of shape and topology optimization problems, comparison of results, and the physical fabrication of hybrid-manufactured products. Ongoing work is aimed at rigorous comparison between candidate constraint generation strategies and the properties of the constraint mapping.