Great Neck, NY · Since 1999
Garage Door Parts Glossary: Every Part, Named and Explained
When a technician says your drum is worn or your bottom bracket is loose, here's what they mean. A plain-English guide to every major part of a garage door and opener, and which ones are safe to touch.
By The Best Garage Door · Updated September 2026 · 6 min read
Quick answer: a garage door system has four groups of parts: the counterbalance (springs, cables, drums and shaft) that carries the door's weight; the track system (tracks, rollers, hinges) that guides it; the opener (motor, rail, trolley, logic board, photo-eyes) that moves it; and the seals that keep weather out. The counterbalance parts are under high tension and are for technicians only.
You don't need to know every part name to own a garage door. But it helps when you're describing a problem over the phone, reading a quote, or deciding whether a job is safe to do yourself. Here's the vocabulary, from the top of the door down.
How the parts fit together
Picture a standard two-car sectional door on a North Shore colonial, seen from inside the garage:
- Above the door, a steel shaft runs the width of the opening. Torsion springs wrap around it, and a cable drum sits at each end.
- A lift cable runs from each drum down to a bottom bracket on the lowest section of the door.
- The door's sections are joined by hinges, and rollers ride in a track on each side that curves from vertical to horizontal.
- The opener hangs from the ceiling, with a rail running to the door. A trolley on the rail connects to the top of the door with a door arm.
- Two photo-eyes sit a few inches off the floor on either side of the opening.
Springs
- Torsion spring
- A large coiled spring mounted on the shaft above the door. It's wound (twisted) so that it turns the shaft and drums to lift the door. Most sectional doors use one or two. A broken torsion spring shows a visible gap in the coils.
- Extension spring
- A long spring that runs parallel to the horizontal track on each side and stretches as the door closes. Common on older and lighter doors. DASMA says extension springs need a safety cable running through the spring so that a broken spring can't whip loose.
- Enclosed or tube-style torsion systems
- Some manufacturers house springs inside a tube on the shaft. Wayne Dalton's TorqueMaster, for example, seals the springs inside a steel tube and includes an anti-drop device intended to stop the door from falling if a spring breaks while the door is up. These systems use brand-specific parts and winding methods.
- Cycle rating
- How many open-and-close cycles a spring is designed for. Manufacturer specifications from Clopay and C.H.I. Overhead Doors describe 10,000 cycles as the industry standard, with upgrades available to 25,000, 50,000 or more. See how long garage door springs last.
- Winding cone
- The cast end of a torsion spring with holes for winding bars and set screws that lock it to the shaft. This is where the stored energy is controlled, and it's the most dangerous part to handle.
Spring color codes
The Door & Access Systems Manufacturers Association publishes an official color code (Technical Data Sheet #171). The paint on the spring means different things for each type:
| Spring type | Color identifies | Examples from DASMA TDS 171 |
|---|---|---|
| Torsion | Wire diameter | .2187" white, .2253" red, .2437" green, .2500" gold, .2625" blue |
| Extension | Door weight, in 10-lb steps | 100 lb tan, 150 lb red, 200 lb tan (colors repeat every 100 lb) |
| Either | Black = unspecified or not on the list |
DASMA's example: two tan extension springs are required to lift a 100-pound sectional door. Its caution is important too: color codes should be confirmed with physical measurements and door weight, especially on older installations. Paint fades, and springs aren't always what the color suggests. That's one reason spring sizing is best left to a technician.
Cables, drums and pulleys
- Lift cable
- Braided steel cable that connects the counterbalance to the bottom of the door. On torsion systems it winds onto the drums. Frayed or loose cables are a stop-using-the-door problem. See cable repair.
- Cable drum
- A grooved spool at each end of the torsion shaft. As the shaft turns, the cable winds onto the drum and lifts the door. A cable that jumps its groove can leave the door hanging crooked.
- Torsion shaft (tube)
- The steel bar the springs and drums mount on.
- Bearing plates and center bearing
- Brackets that support the shaft at the ends and the middle, with bearings so it turns smoothly.
- Pulley (sheave)
- On extension spring doors, pulleys route the cable from the spring to the bottom bracket. Worn pulleys squeal and can crack.
- Bottom bracket
- The fitting at each bottom corner of the door where the cable attaches. DASMA warns these are under extreme tension. Never loosen them.
Tracks, rollers and hinges
- Vertical and horizontal track
- The steel channels on each side. The door travels up the vertical track, around the radius (curve) and back along the horizontal track.
- Rollers
- Wheels on stems that ride in the track. Steel rollers are common on basic doors; nylon rollers run quieter. See roller replacement and making a door quieter.
- Hinges
- Join the sections so the door can bend around the curve. They're numbered by position; the ones at the bottom corners work with the bottom bracket.
- Sections (panels)
- The horizontal pieces that make up a sectional door. A damaged section can sometimes be replaced if the model is still made.
- Strut (reinforcing bar)
- A steel brace across a section, often the top one, to keep wide doors from bowing, especially where the opener arm attaches.
- Jamb brackets and back hangs
- Hardware that fastens the tracks to the door frame and hangs the horizontal tracks from the ceiling.
A roller out of the track or a bent track means the door is off track. Don't keep running it.
Opener parts
- Motor unit (powerhead)
- The box on the ceiling with the motor, gears, lights and logic board. Wall-mount (jackshaft) openers put the motor beside the door on the torsion shaft.
- Rail
- The long beam from the motor to the door, carrying a chain, belt or screw drive.
- Trolley (carriage)
- Rides along the rail and connects to the door. The emergency release cord, usually with a red handle, hangs from it. See opening the door without power.
- Door arm (J-arm)
- The curved and straight arm linking the trolley to the door bracket on the top section.
- Logic board
- The opener's circuit board. It reads remotes and sensors, sets travel and force, and shows diagnostic codes. Our LiftMaster error code guide explains them.
- Learn (program) button
- Used to pair remotes and keypads. On LiftMaster and Chamberlain openers its color identifies the radio technology. See programming remotes and keypads.
- Safety sensors (photo-eyes)
- A sending and a receiving eye near the floor that stop and reverse a closing door when the beam is broken. See sensor lights explained.
- Wall control
- The button inside the garage. Many include a light switch and a lock (vacation) mode.
- Battery backup
- A rechargeable battery in some openers that runs the door during outages.
Seals and weatherstripping
- Bottom seal (astragal)
- The rubber or vinyl strip along the bottom edge of the door that seals against the floor.
- Retainer
- The aluminum channel on some doors that holds a replaceable bottom seal.
- Perimeter weatherstrip (stop molding)
- Flexible seal along the sides and top of the door frame.
- Section seals
- Seals between sections on some insulated doors.
- Threshold seal
- A strip fixed to the garage floor to close gaps on uneven slabs.
Which parts are DIY-safe?
| Generally homeowner-friendly | Technician only |
|---|---|
| Lubricating hinges, roller bearings, springs | Torsion and extension springs |
| Aligning and cleaning photo-eyes | Lift cables and drums |
| Replacing remote, keypad and backup batteries | Bottom brackets and bottom-corner rollers |
| Programming remotes and keypads | Winding cones, shaft and bearings under tension |
| Replacing perimeter weatherstrip | Straightening bent track or resetting an off-track door |
| Tightening hinge and track bracket bolts | Opener force settings and logic board replacement |
The rule of thumb: if a part is connected to a spring or a lift cable, don't loosen it. DASMA warns that springs are under high tension and should only be adjusted by qualified individuals.
For a routine that covers the safe items, see our maintenance checklist.
Need a part replaced? The Best Garage Door repairs springs, cables, rollers, tracks and openers across Great Neck and the North Shore. Every repair comes with a price confirmed before work starts and a written parts and labor warranty. Book online or text a photo to (929) 206-7699.
Questions
Frequently asked questions
What are the two types of garage door springs?
Torsion springs mount on a steel shaft above the door and twist to lift it. Extension springs run along the horizontal tracks on each side and stretch to lift it. Most sectional doors today use torsion springs; extension springs are more common on older and lighter doors.
What do the colors on garage door springs mean?
Under DASMA's official color code (Technical Data Sheet 171), the color on a torsion spring identifies its wire diameter, and the color on an extension spring identifies the door weight it's rated for. Black means the size isn't on the list. DASMA cautions that colors should be confirmed with actual measurements.
What is a bottom bracket on a garage door?
The bottom bracket is the metal fitting at each bottom corner of the door where the lift cable attaches. It's connected to the spring system under tension, and DASMA warns that bottom brackets are under extreme tension. Homeowners should never loosen or remove them.
What is the trolley on a garage door opener?
The trolley, or carriage, is the part that rides along the opener rail and connects to the door through the door arm. The emergency release cord hangs from it. Pulling the cord disconnects the trolley so the door can move by hand.
Which garage door parts can I replace myself?
Generally safe for homeowners: weatherstripping, the bottom seal on many doors, safety sensor alignment, remote and keypad batteries, opener light bulbs and lubrication. Leave springs, cables, drums, bottom brackets and anything under spring tension to a trained technician.
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