Yale Lock Manufacturing Company v. Sargent was a United States Supreme Court case in which the Court held that a patentee may not use a patent to prevent others from making a product that is not covered by the patent. The case involved a dispute between Yale Lock Manufacturing Company and Sargent, a competitor. Yale had a patent for a particular type of lock, and Sargent was making a similar lock that was not covered by the patent. Yale sued Sargent for patent infringement, but the Supreme Court held that Yale could not use its patent to prevent Sargent from making a product that was not covered by the patent. The Court reasoned that a patentee should not be able to use a patent to prevent others from making a product that is not covered by the patent. The Court noted that a patentee should only be able to use a patent to prevent others from making a product that is covered by the patent. In conclusion, the Supreme Court held that a patentee may not use a patent to prevent others from making a product that is not covered by the patent. This case established an important precedent that has been followed in subsequent cases.

In the case of Yale Lock Manufacturing Company v. Sargent, the Supreme Court was tasked with determining whether a patent for an improved lock mechanism held by Yale Lock Manufacturing Company (Yale) had been infringed upon by Sargent's similar product. The majority opinion found that there was no infringement because although both locks were similar in design and function, they operated differently due to differences in their internal mechanisms. However, Justice Field dissented from this decision on the grounds that he believed it should be up to a jury to decide if there had been any infringement or not. He argued that while it may have appeared at first glance as though there were no substantial differences between the two products, only an examination of each device could reveal which parts constituted protected elements under patent law and which did not. Therefore, he concluded that since questions of fact remained unresolved regarding how much similarity existed between these two devices and what specific features constituted protected elements under patent law, it would be inappropriate for the court to make such determinations without allowing a jury trial first.