Abstract: A roll-up door in which the bottom bar is attached to the flexible door curtain has a transverse opening at an end adjacent to a jamb of the frame of the door. A breakaway shaft travels in a track in the jamb and has one end that normally seats in the transverse opening and provides a link between the bottom bar and the jamb. The other end of the shaft is restrained so that the shaft is held in a generally horizontal attitude. The opening in the bar and the breakaway shaft have cooperating means to normally retain the shaft in the opening but which are releasable upon a force striking the curtain or bottom bar. The breakaway shaft will separate from the bar upon impact thereby freeing the bar from engagement withthe jamb and preventing damage. The breakaway shaft may thereafter be reinserted into the opening in the bar to reconnect the bottom bar to the track and permit continued operation of the door.