Valu Engineering, Inc. (Valu) (plaintiff) manufactured guide rails for conveyors that were primarily used in bottling and canning plants. Valu’s guide rails helped products stay on the moving conveyors in plant areas that were frequently washed and sanitized, sometimes referred to as wet areas. Wet areas required parts made of corrosion-resistant materials, like steel or plastic. Valu’s promotional materials described the functional advantages of its guide rails. Valu also applied for a patent for the guide rails that described their usefulness, but Valu abandoned the patent application. Valu later applied for a trademark for three of its guide-rail designs. Valu’s trademark application was approved by the examining attorney. Examining attorneys are individual attorneys who handle the initial examination of trademark applications. Rexnord Corporation (Rexnord) (defendant) then filed an opposition to Valu’s trademark application. Rexnord argued that Valu’s designs for guide rails could not be registered as trademarks because they were functional. The Trademark Trial and Appeal Board (Board) sustained Rexnord’s opposition. The Board found that Valu’s guide-rail designs had utilitarian advantages in the wet areas of bottling plants. This functionality made Valu’s designs ineligible for trademark protection. Specifically, the Board found that the following evidence showed that Valu’s designs were primarily functional: (1) Valu’s prior patent application, (2) Valu’s advertising materials, (3) Valu’s limited range of designs, and (4) the economic benefits to customers of using Valu’s guide rails. Valu appealed, arguing that the Board improperly assessed only the wet-area uses rather than assessing all possible uses of Valu’s guide-rail designs.