Repairing a garage door
Garage doors have 2 main components, the door itself and the opener. If the door needs repairing whether it lifts in sections or in one piece it works on spring tension. There will be metal tracks on the wall that the door moves on and a heavy spring(s) provide the power. Most door failures can be repaired simply.
First, check the metal tracks, are the mounting brackets tight, are there any dents, crimps or flat spots, if either then a repair can be done. If the tracks are badly damaged then they would need to be replaced. Checking that the tracks are aligned correctly with a level, horizontal tracks should slant down slightly at the back whereas with roll-up doors the vertical sections of the track should be plumb. They should also be at the same height. If they are not aligned correctly then the mounts should be loosened but not removed and the tracks should be gently realigned.