Will a garage door go back up if it hits something?

Yes, a properly working garage door will reverse and go back up if it hits something while closing. Federal regulations since 1993 have required all residential garage door openers to include two safety reversal systems: the photo-eye sensors near the floor that reverse the door if their beam is interrupted, and a mechanical force-sensing system in the opener that reverses the door if it meets resistance while closing. To test the mechanical system, place a 2x4 flat on the floor under the center of the door and run the door down. It should hit the wood and immediately reverse to the open position. If it does not reverse, the close-force setting on the opener is too high and needs adjustment.