Main tees should always run at right angles to the joists in the room. Locate the position of each main tee by stretching a tight line from the top edge of the wall angle on all sides of the room at each position where the main tees are to be placed.
Now, cut the suspension wires to the proper length. The wires should be 12 inches longer than the distance between the old ceiling and the new guideline string. Locate the first suspension wire for each main tee directly above the point where the first cross tee meets the main tee. Check the original sketch of the room to determine this location. Be sure the suspension wires are securely fastened. Apply them to the ceiling with screw eyes, screw hooks, nails, or by drilling. Attach a suspension wire every 4 feet along the level guideline. Stretch each wire to remove any kinks and make a 90-degree bend where the suspension wire crosses the level line.