Wainscoting Designs, Layouts, and Materials

Any run of floor, old or new, invariably has high and low spots, even if the difference is only 1/8 inch. So you can't just cut all the beadboards the same length and assemble from the baseboard up. You must find the high spot and mark the chair-rail level line from there. To keep the top of the baseboard level, shim as needed, then, using a block equal to the height of the gap, scribe and cut the bottom edge to match the floor's ups and downs.