Most jurisdictions bar the issue of a patent to an inventor who has publicly used or demonstrated the invention before the application date of the patent. In the United States, the public use bar comes into effect one year after such a public use under 35 U.S.C. § 102 – this “grace period” does not necessarily exists in all legal systems. For this reason, patents should always be applied for before public use at, for example, trade shows. An exception often exists for Experimental Use, i.e., testing of the invention.