||06-17-2011 03:32 PM
The end cuts on the mains will only "go up square automatically" if your walls are perfectly square. Not usually the case. Measure an equal border on either end of the room from the wall to the center of the main runner. Make a small mark on the wall angle.Take a piece of thin string (available at HD or Lowes in the ceiling dept.) and run the length of the room. You can tie the string to a small nail (I usually use a pop rivet) and push it behind the wall angle. This will get the main straight. I can assure you the tees going to the wall will vary in length. Do the same thing with the border tees. Pull a string that direction also. Your main ends will vary also I can almost guarantee. You can trim the ends somewhat to try to square things up, but you're limited by the width of the wall angle (7/8"). It is best to pop rivet all of the main ends and every other 2' or 4' tee to the wall angle to keep them from moving so things stay square. You may get by with adjusting if the ceiling isn't too far out....
Best of luck.