Garage Door Glossary

Garage door pros use a lot of jargon. This glossary defines the parts, opener features, door types, dock equipment, and code terms in one or two plain sentences. Family-owned and serving the Mid-Atlantic since 2004, First Choice Garage Doors wrote these the way we'd explain them at your house. 54 terms, defined.

Door parts & hardware

Counterbalance system

The springs, cables, and drums that store energy and do the actual lifting of a garage door, so the opener only has to nudge a balanced door. When it's off, the door feels heavy or won't stay open. Related: Diagnose a door that won't open →

Torsion spring

A tightly wound spring mounted on a shaft above the door that unwinds to lift it. The most common spring type and the part that most often breaks (often with a loud bang). Under high tension — not a DIY part.

Extension spring

Long springs mounted along the horizontal tracks that stretch and contract to counterbalance the door. Common on older or lighter doors; should have safety cables.

Lift cable

Steel cable that runs from the bottom bracket to the cable drum, transferring spring force to the door. Frays or snaps with age and rust (faster in coastal salt air).

Cable drum

The grooved wheel at each end of the torsion shaft that winds the lift cable as the door rises.

Roller

The wheels that let the door glide in the tracks. Worn nylon or rusty steel rollers make a door noisy and rough.

Track

The metal channels (vertical and horizontal) that guide the rollers and hold the door's path. Bent tracks cause binding and "off-track" doors.

Hinge

Connects the door sections and lets them pivot as the door bends around the track curve.

Bottom bracket

The fitting at the bottom corners that anchors the lift cable. Under spring tension — do not loosen it.

Bottom seal / astragal

The flexible strip along the bottom edge that seals against the floor to keep out water, drafts, and pests. Related: Repair or Replace? →

Weatherstripping (weather seal)

Seals around the sides and top of the door (and between sections) that block weather and energy loss.

Strut

A horizontal reinforcing brace added across a door section for rigidity and wind resistance.

Bearing plate / center bearing

Brackets and bearings that support the torsion shaft as it turns.

Garage door openers

Garage door opener

The motor unit that opens and closes a (spring-balanced) door and holds it in place. It does not do the heavy lifting — the springs do. Related: Opener Not Working? →

Trolley (carriage)

The piece that travels along the opener rail and connects to the door arm to push/pull the door.

Belt / chain / screw drive

The three ways an opener moves the trolley: belt (quietest), chain (cheapest), screw (fewer parts). Related: Belt vs. Chain vs. Screw →

Jackshaft (wall-mount) opener

An opener mounted on the wall beside the door instead of on the ceiling — great for high ceilings or overhead storage.

DC motor / AC motor

DC motors are quieter, allow soft start/stop and battery backup, and are standard on modern openers; AC is older and louder.

Soft start/stop

A DC-opener feature that ramps the door's speed up and down smoothly for quieter, gentler operation.

Limit settings

The programmed stop points that tell the opener exactly where "fully open" and "fully closed" are.

Force settings

How much resistance the opener tolerates before reversing; set too high it's unsafe, too low it reverses for no reason.

Photo-eye (safety sensor)

Paired sensors near the floor that project an invisible beam; if anything breaks the beam, the door won't close (or reverses). Required since 1993. Related: UL 325 Opener Safety →

Auto-reverse

The federally required safety feature that makes a closing door reverse if it contacts an object or its beam is broken.

Rolling code

Security technology that changes the remote's code every use so it can't be copied — far safer than old fixed-code remotes.

HomeLink

The built-in garage button in many vehicles that pairs with your opener.

Battery backup

A battery that runs the opener during a power outage; required on new residential openers in some states.

Emergency release (red cord)

The red handle that disconnects the door from the opener so you can operate it by hand. If pulled, the motor runs but the door won't move.

Smart (Wi-Fi) opener

An opener connected to your home network and an app for remote control, status, and alerts. Related: Automation Explained →

myQ

The app/platform for LiftMaster and Chamberlain smart openers. Related: Smart Opener vs. Retrofit →

Keypad

A wireless code pad mounted outside the garage for keyless entry.

Door types & materials

Sectional door

A door made of horizontal panels that roll up overhead on tracks — the most common residential and warehouse style. Related: Commercial Doors Explained →

Rolling (coiling) steel door

Interlocking slats that coil into a barrel above the opening; space-saving and very secure. Related: Commercial Door Types Compared →

High-speed door

A fabric or rubber commercial door that opens several feet per second to control airflow, temperature, and traffic.

Fire-rated door

A door (usually rolling steel) that closes automatically in a fire to maintain a building's fire separation, where code requires it. Related: Fire-Rated & Commercial Code →

Counter shutter

A small rolling door for service counters, concessions, and pass-throughs.

Full-view (aluminum & glass) door

A modern door with aluminum frames and glass panels; lightweight and contemporary, less insulating.

R-value

A measure of a door's insulation; higher means better resistance to heat flow. Matters most on attached or conditioned garages. Related: Repair or Replace? →

Polystyrene vs. polyurethane insulation

Two insulation types inside a door: polystyrene (panel foam, moderate R-value) and polyurethane (foamed-in-place, higher R-value, stronger and quieter).

Commercial & loading dock

Dock leveler

The adjustable platform that bridges the height and gap between the dock floor and a trailer bed. Comes in mechanical, hydraulic, air-powered, and edge-of-dock types. Related: Loading Dock Explained →

Dock seal

Foam compression pads the trailer presses against to close the weather gap; best for consistent trailer sizes.

Dock shelter

Fabric curtains that frame the opening to seal around a range of trailer sizes. Related: Dock Buyer's Guide →

Vehicle (trailer) restraint

A hook or barrier that locks a trailer to the dock so it can't roll or pull away during loading — the main defense against trailer-separation injuries.

Dock bumper

Rubber blocks that absorb trailer impact and protect the building face and leveler. Cheap to replace; expensive to ignore.

ICC bar (rear impact guard)

The steel bar across the back of a trailer that vehicle restraints latch onto.

Code, safety & permitting

UL 325

The safety standard requiring residential openers to have auto-reverse and photo-eye protection (in effect since 1993). Related: UL 325 Explained →

Wind load (wind-rated)

A door's engineered ability to resist wind pressure; coastal zones require wind-rated doors by code. Related: Wind-Load & Impact-Rated Doors →

Impact-rated

A door tested to resist windborne debris in hurricane/coastal zones (often paired with wind rating).

Design pressure (DP)

The specific positive/negative wind pressure a door is rated to withstand, used to match a door to local code.

DASMA

The Door & Access Systems Manufacturers Association, whose standards and ratings (e.g., for wind load) are widely referenced.

AHJ (Authority Having Jurisdiction)

The local building department, inspector, or official who enforces code and issues permits where you live. Related: Permits & Code Compliance →

Permit

Local government authorization to do certain work; a full door replacement often needs one. Related: Do You Need a Permit? →

NFPA 80

The fire-door standard that governs installation, inspection, and annual testing of fire-rated doors. Related: Fire-Rated & Commercial Code →

PA Uniform Construction Code (UCC)

Pennsylvania's statewide building code, enforced at the municipal level — so permitting in PA happens through your town/township.

HOA approval

Some homeowners' associations require approval of a door's style or color before replacement, separate from any government permit.

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