Torsion springs are typically mounted horizontally above the garage door, although on older homes with smaller garages they can sometimes be mounted at the back. As the garage door lowers, cables attached to the bottom corners of the garage door wind the springs up, creating stored energy. When it’s time to open the garage door, this stored energy is used to unwind the spring and lift the door.
The less common type of garage door spring is an extension spring. You’ll usually find them located above the door track, although occasionally they will be mounted to the side vertically. This system uses springs that are attached to cables, which are attached to the bottom corners of the garage door. When the garage is closed, the springs are stretched, or extended, and the energy stored in the extended springs is what lifts the garage door back up.
infographic by: garagedoorrepairpros.ca