Garage Door Troubleshooting

Garage door anatomy: what every part is called

Naming the part you are looking at makes every other conversation easier — with us, with a home inspector, with a warranty department. The terms below follow DASMA’s own industry terminology, with the everyday word first where the two differ.

Every part, in order

1. 1 Section (panel) — One of the horizontal sections the door is built from. Most residential doors have four, joined by hinges so they can pivot as the door rolls overhead.
2. 2 Torsion spring — Wound spring above the opening that counterbalances the door’s weight. Under high tension at all times — removal, repair and adjustment are technician work.
3. 3 Torsion shaft — The shaft that transfers torque from the springs to the cable drums. Torsion springs are mounted on this shaft, which DASMA notes inherently provides containment if a spring breaks.
4. 4 Cable drum — Grooved drum at each end of the shaft. It winds the lift cable up as the door opens and pays it out as the door closes.
5. 5 Lift cable — Runs from the drum down to the bottom bracket on each side. Frayed or worn cable is a replace-it item, and DASMA says only a trained technician should do it.
6. 6 Bottom bracket under spring tension — The loaded one. The bottom bracket is connected directly to the counterbalance system, so it carries the full spring load whenever the door is down. DASMA is explicit: these brackets “should be adjusted or loosened only by a trained door systems technician,” and many manufacturers now fit tamper-resistant hardware here. Loosening one is how people get badly hurt.
7. 7 Top fixture — Bracket at the top corner of the top section. It holds the top roller and sets how the door meets the header when it closes.
8. 8 Graduated edge hinge (end hinge) — Hinge on the edge of the sections. It holds a track roller and is numbered so it goes back in the right place — that numbering is what makes the closed door sit flush against the jambs.
9. 9 Center hinge (intermediate hinge) — Joins one section to the next across the face of the door and lets them pivot as the door rolls into the horizontal track.
10. 10 Roller — Rides inside the track. On a healthy door you can slide and turn the roller stem in its bracket by hand — if you cannot, something is bent or bound.
11. 11 Vertical track — The straight run beside the opening. It is deliberately tilted back a little so the door does not rub the opening on the way up.
12. 12 Horizontal track — Carries the door back over your head. Its slight upward slope helps start the door down and helps keep tension on the cables.
13. 13 Track bracket — Fastens the vertical track to the jamb. These have to land in solid wood — DASMA has a whole sheet on why mounting into drywall alone is a problem.
14. 14 Strut (reinforcement) — Stiffener across a section that reduces how much it sags when the door is overhead, and adds wind-load capability.
15. 15 Bottom seal (astragal) — The compressible seal along the bottom edge that closes against the floor. In Arizona it is usually the first rubber part to go hard and shrink.
16. 16 Header seal — Seals the top of the opening against weather and light infiltration.
17. 17 Jamb seal — The seal down each side of the opening, usually nailed to the jamb outside the door. Also called stop moulding.
18. 18 Photo-eye sensors — The entrapment-protection beam across the bottom of the opening. Per the DASMA checklist the beam should sit no higher than six inches above the floor.
19. 19 Opener rail — The rail the opener’s trolley travels along, running from above the opening back to the power unit.
20. 20 Trolley — The carriage on the rail that connects to the door arm. Disconnecting it is what puts the door back on manual.
21. 21 Manual release handle (red) — UL 325 requires this handle to be red and easily told apart from the rest of the opener. It should be reachable and no more than six feet above the garage floor.

Terminology from DASMA Technical Data Sheet #160, Sectional Garage Door Terminology (dasma.com). DASMA states the sheet “is not to be construed as a standard-type document” and that the terms “are not universal” — manufacturers vary. Photo-eye and manual-release dimensions are from DASMA TDS #167 (checklist for home inspectors and consumers).