Two kinds of cable
On a torsion door, one lift cable on each side runs from the bottom corner of the door up to a drum on the spring shaft. As the springs turn the shaft, the drums wind the cables in and the door rises.
On an extension-spring door, each lift cable runs from the bottom corner over pulleys to its spring. A second, separate cable, the safety containment cable, runs through the middle of each spring and is anchored at both ends, so a spring that breaks stays on it.
- Not sure which springs you have? How to tell torsion from extension.