Edward Phillips (plaintiff) invented and obtained the ‘798 patent for modular, steel-shell panels that could be welded together to form vandalism-resistant, load-bearing, and impact-resistant walls. After Phillips obtained the patent, he entered into an agreement with AWH Corporation (defendant) and two other companies to market and sell the panels. That relationship ended, but Phillips received an AWH sales brochure the following year that led Phillips to believe that AWH was continuing to use his patented technology without his consent. Phillips sued AWH for infringement in the U.S. District Court for the District of Colorado. Claim 1 of the ‘798 patent stated: “further means disposed inside the shell for increasing its load bearing capacity comprising of internal steel baffles extending inwardly from the steel shell walls.” The district court construed the claim language as a means for performing a function of the invention, which invoked 35 U.S.C. § 112, paragraph 6. Section 112 provides that a claim “shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.” After reviewing the ‘798 patent specification, the court concluded that a “baffle” was required to “extend inward from the steel shell walls at an oblique or acute angle to the wall face,” and that the allegedly infringing product did not have “baffles.” The district court granted AWH’s motion for summary judgment of non-infringement, and Phillips appealed. A divided panel of the appellate court affirmed. The appellate court then vacated the appellate panel's judgment and reheard the case en banc.