The basic concept and operation of a garage door and its spring(s) remain the same throughout all brands and types of doors. An over-the-door assembly is connected to the upper corners of the garage door, running parallel with two or more torsion springs that transfer garage door opener torque from the trolley assembly to the door itself. The torsion springs are twisted via an electric or hand-crank garage opener, winding up the stored tension in the coil(s). When the door is opened, gravity pulls down on it, causing its weight to overcome the rubber-coated torsion springs' resistance to twisting.
The springs extend, winding up their stored tension even more to allow the door weight to be fully suspended. When the garage door is closed, the torque from the torsion spring(s) rotates the trolley assembly away from the top of the tracks, removing all stored tension in the torsion spring(s).