A design patent is cheap, narrow, and quietly one of the most dangerous instruments in the patent system, because a single ornamental claim can capture an infringer's entire profit on a product. This library article follows a design case from beginning to end: how a court construes a claim built of drawings, how the ordinary-observer test descended from Gorham Co. v. White and made sole by Egyptian Goddess v. Swisa decides infringement, and how functionality and the post-LKQ obviousness standard now threaten validity. It explains 35 U.S.C. § 289's total-profit remedy and how Samsung Electronics Co. v. Apple Inc. reworked the "article of manufacture" question that determines the size of the base. Along the way it covers willfulness, the marking trap, injunctions, and the International Trade Commission, with invented worked examples grounding each doctrine. Read it before you assert or defend an ornamental claim.