A "public use" under pre-AIA 35 U.S.C. 102(b) occurs when the invention is in public use before the critical date and is ready for patenting. The Federal Circuit has explained that the proper test for the public use prong includes two key elements: The purported use was accessible to the public; or The invention was commercially exploited. As stated in MPEP 2133.03(a): "The proper test for the public use prong of the [pre-AIA] § 102(b) statutory bar is whether the purported use: (1) was accessible to the public; or (2) was commercially exploited. Commercial exploitation is a clear indication of public use, but it likely requires more than, for example, a secret offer for sale." It's important to note that even a single public use can trigger the statutory bar. The use does not need to be widespread or involve multiple instances to constitute a public use under the statute. To learn more: public use pre-AIA 102(b) statutory bar patent law commercial exploitation