A method is described for measuring a dimension on a substrate, wherein a target pattern is provided with a nominal characteristic dimension that repeats at a primary pitch of period P, and has a pre-determined variation orthogonal to the primary direction. The coding pattern has target elements and data elements. The primary image may depict an article of manufacture. Once the off center drain aperture is aligned with the underlying drain with the perimeter of the center section aligned with the aperture in the surrounding material, the center section is placed into the similarly shaped aperture and fixed in position with adhesive or grout and the drain strainer may be mounted into the off center drain aperture.