The link below will open a picasa web album which will show a repair to a fuhr patio door. This particular door was controlled by a drive gear. The drive gear was connected to teh corners by teeth & connection. sometimes the gear box snaps, or the teeth part opens or breaks. this one had teh teeth connection open. this system is now not produced no more. you can though repair them using the shown method........
http://picasaweb.google.com/UKWDTC/FUHR ... 72jkgjFn8w
Don