Launching a product that reads on someone else's valid patent invites an injunction, a damages award that can run into nine figures, a fee-shifting order, and—if the infringement is willful—trebled damages, which is why disciplined teams assess that exposure before launch through a freedom-to-operate (FTO) analysis. This UpLaw guide walks the entire workflow through a fictional smart-lock startup: separating FTO from patentability, defining the product's technical scope, searching and triaging the patent landscape, construing claims under Phillips and Markman, building claim charts, and testing both literal infringement and the doctrine of equivalents against the limiting doctrines of estoppel, dedication, and ensnarement. It then works through validity under Sections 101, 102, 103, and 112, explains how Halo and Section 298 make opinions of counsel valuable but never mandatory, and shows why a clean non-infringement opinion usually beats an invalidity one—especially against an inducement claim after Commil. It closes with design-arounds, licensing, exhaustion, the distorting economics of patent-assertion entities, and how to document the work and communicate risk as a calibrated judgment rather than a false promise of safety.