STEP 3. Having established the proper starting point, lay out two chalk lines at right angles to make sure the room is square. See figure 1 for exact procedure. Chalk lines must be used as control lines for installing the access floor. The reason for laying chalk lines for installing the access floor. The reason for laying chalk lines rather than just measuring from the walls is that the walls are not always square. The chalk line system gives a square reference point. Be careful to keep the access floor square at all times during installation.

NOTE: When starting the installation in the corner of a room, stretch a dry line for line "B" before laying down chalk. Check the distance from "B" line and the "A" chalk line to the walls. If the distance to the walls is over 24 inches at any point, move the entire line closer to the wall so that the greatest distance is 24 inches or less (See figure 1.)

Step 4. Check Control Lines