This is UpLaw's deep case-law treatment of trade dress protection for product design and configuration—the corner of trademark law shaped almost entirely by four Supreme Court decisions handed down between 1992 and 2001. It walks Two Pesos, Qualitex, Wal-Mart v. Samara, and TrafFix holding by holding, then maps how the federal circuits have applied their two great gatekeepers: the rule that product design is never inherently distinctive and always demands secondary meaning, and a functionality doctrine that quietly decides most configuration cases. The article explains the outcome-determining line between product packaging, product design, and the packaging-like tertium quid; works through utilitarian functionality under Inwood, the Morton-Norwich factors, and aesthetic functionality under Qualitex; and surveys the circuit split over alternative-design evidence after TrafFix. It covers who bears the burden of proving (non)functionality, why registration changes that allocation, and how Daubert gatekeeping of surveys and experts decides close cases. Two invented hypotheticals, an offense-and-defense business playbook, an industry tour, a comparative look abroad, and a practical FAQ round out the treatment. The throughline stays in view: the law's effort to balance brand identity against the public's right to copy unpatented, useful features.