It was mentioned to place clamps in the overhead door track to keep the door from being raised from the outside. One other way to limit access is that you can put a padlock through the holes in the track to prevent the door from being opened from the inside. That way if someone gets in it's harder for them to remove large stuff from the shop. They could always cut the lock but if you use matched padlocks on both sides of the door it will hopefully take them more time than they want to spend.
Rob
Rob