Now that you've attached the fasteners and hanger wire using the instructions in part 6, it's time to stretch some reference strings. They will run exactly at the level of the bottom of the wall moldings to show you where to put the runners and cross tees and serve as guides for cutting.
To stretch these strings, choose the corner of the room where you plan to start your installation. You will stretch only two strings: string AB, which will be the border tile distance from the one wall (14 inches in our example); and string CD which will be the border tile distance from the other wall.
Be sure the strings are at the level of the bottom of the wall molding so they will be out of the way while you install the grid. Check your strings with a framing square to be sure they are square. Adjust until they are, even if the border tiles will be irregular to accomplish this.