To get off to a perfect start, you may have to adjust the first strip to compensate for a corner that's out of plumb. Hold the strip tight against the wall and adjust it until a level shows it's plumb. Measure the size of the gap that results (left). Then, starting at the end of the strip that's touching the wall, cut it lengthwise so it tapers from the amount of the gap to the strip's full width. The strip will fit the angle of the wall while remaining plumb.