United States Gypsum developed a new putty to use on walls and ceilings to cover cracks. A key ingredient in the compound was a silicon product made by another company. The patent application did not list that as an ingredient in the putty. A competitor started to make and sell the same putty, and the two companies ended up in court.

Could USG win for patent infringement? [United States Gypsum v. National Gypsum, 74 F.3d 1209, Fed. Cir. (1996)].