Abstract: Disclosed herein are methods and tools for customizing shower panels to accommodate a variety of shapes and sizes of shower bases, where such methods and tools reduce installation steps. One exemplary method includes steps of using tools to trim a back shower panel, a first side shower panel, and a second side shower panel to conform to the contours of the top edges of a shower base. An exemplary assembly of tools used to perform described methods includes a plurality of contour gauge tools and a drain center groove. Each contour gauge tool includes a contoured edge, a slot formed through the contour gauge tool, and indicia formed on a surface of the contour gauge tool. The drain center tool includes a first groove, second groove intersecting the first groove and perpendicular to the first groove, and a tab extending upward of the top surface of the drain center tool.