Measure the tile border pieces and mark the back side of the tile at a 45-degree angle. To measure the tile length properly, mark where the bottom edge of the border tile meets the outside edge of the main tile. Apply masking tape on either side of the cutting line on both sides of the tile to protect the finish.
Cut the border tile carefully with the wet saw. Wear safety glasses and keep your fingers a safe distance from the saw blade. Cut the tile completely to reduce the chance of a rough edge or chipped corner.
Remove the masking tape and inspect the tile on the finished side for any large chips or imperfections that require you to cut another tile. If the cut edge has any rough spots, smooth them carefully with the tile file. Place the cut tile in its intended space without any adhesive to verify you cut it properly before actually installing it.
Apply adhesive to the wall using the notched trowel. Place the tile and tile spacers so that the tiles are equally spaced and the grout lines are straight.