Residential Garage Door Terminology

Download a PDF version of this page: Residential Glossary of Garage Door Terms.


Air Infiltration: The leakage or passage of air through a door system

Anodize: A hard non-corrosive oxide film on the surface of aluminum

Astragal: A compressible or deformable seal provided on the bottom edge of a door

Astragal Retainer: A component, mounted to the bottom edge of a door, that holds an astragal in place

Automatic Opening Device: Quick opening mechanism recommended for installations requiring rapid automatic door opening without use of an electronic operator


Back Hang: Hanger fabricated from angle iron, which attaches the end of the horizontal tracks to roof construction or ceiling

Back Jamb: Wood member on the inside surface of the garage, surrounding the door opening

Backroom: Horizontal distance measured into a building from the door mounting surface to the first obstruction within the zone required to install or operate the door

Bead: A strip of metal, vinyl, or rubber used to secure glass around the periphery of a pane

Bottom Bracket: A structural support located predominantly on the bottom section that holds track rollers and may also provide for attachment of lifting cables. Bracket locations other than at bottom section corners are possible

Bottom Weatherseal: Astragal or other weatherstrip attached to the bottom of a door to seal against the floor

Bow: Condition where a garage door bottom rail of wood is not level or straight, which is characterized by a closed door “smiling” (corners turned up)

Bracket Mounted: Method of fastening vertical track or jamb using jamb brackets


Cable Drum: Grooved drum, fitted on torsion spring shaft, onto which lifting cable is wound when door is opened

Cable Drum Set Screws: Normally refer to set screws that attach the drum to the shaft/tube. One screw may secure the cable to the drum in order to secure proper cable length

Cable Safety Device: A bottom fixture designed to slow or stop the descent of a door in the event of a cable breakage

Cable Stop: A swaged fitting at the end of the cable to prevent slippage through the slot of a drum

Center Bearing Bracket: A bracket that houses a shaft bearing and aligns and supports the torsion shaft and spring(s) assembly. Also serves to anchor the stationary cone(s) to header

Center Hinge: A hinge generally located on the intermediate stiles to allow sections to pivot as door opens. Also used as graduated edge hinge between bottom and intermediate section

Center Stile: Vertical member of a door section which provides structural rigidity and location for center hinge attachment

Clearance: The amount of side room, head room and back room required to properly install a sectional door

Counterbalance System: A system which counteracts the weight of a garage door to allow a reduced force to open and close the door

Cycle: An action on the door from the fully closed position, to the fully open position, and returned to the fully closed position


Design Wind Load: Horizontal design load applied to a garage door based on such factors as wind speed, building height and horizontal door location

Door Casing: The framing members which a door opening is finished

Door Frame: The frame into which the door fits; consists of two door jambs, and a door header

Door Jamb: The upright framing on each side of the door opening

Door Size: Door dimensions characterized by the width first and height second

Double Glazing: Use of two thicknesses of glazing within an opening to improve insulating value and/or reduce sound transmission

Double Strength Glass: A grade of window glass lighter than plate glass and usually 1/8″ thick

Double Track Low Headroom: Addition of second pair of horizontal tracks to reduce high point of travel of top section and permit door being mounted in area with minimum headroom facilities

DSB: Acronym for Double Strength Grade B Glass


Electric Operator: An electrically-powered device to control the opening and closing of a door End Stile located at each end of a door section which provides for attachment of graduated edge hinges

Extension Spring: Provides power or tension by stretching or pulling, and is usually mounted along the horizontal section of track extending from front of the door opening to the back hang

Exterior Lock: Keyed lock on exterior of the door


Flag Bracket: See Jamb Bracket

Flush Door: Door comprised of sections unbroken by visible rails and stiles where the facing of the entire door presents an even surface

Front Mounted Low Headroom: Low headroom hardware where springs mount on torsion shaft above opening

Full View Section: Full Vision Section (A totally glazed section with various types of glass or clear plastic. Section formed of aluminum extrusions which will marry with steel or aluminum sections above and below)


Galvanizing: Zinc coating to protect against corrosion

Gauge: U.S. Standard, established by congress in 1893, specifying that weight per square foot would be indicated by a numbering system; larger numbers indicate smaller thicknesses and vice versa

Glazed: Fitted with panes of glass or clear plastic

Graduated Edge Hinge: Hinge placed on edge of door sections allowing sections to pivot as door opens and closes. Hinges hold track roller and are graduated and numbered for correct placement to ensure flush sit of door against jambs when closed

Grille: Insert within a window, designed to give the appearance of divided lines


Header Seal: Weather-stripping mounted at opening header to seal the opening between header and curtain

Headroom: Vertical clear space required above the door opening, and below the lowest ceiling obstruction, required for proper installation and operation of the door and its hardware

High Cycle Spring: Counterbalance springs with increased cycle life capability for high usage doors

High Lift: Distance from header to underside or horizontal track, which high lift is required

High Lift Track: Track and hardware that causes the door to rise vertically some distance above the top of the door opening before it levels out into a horizontal position

Hinge: Hardware item that joins door sections together, and allows sections to pivot independent of each other

Horizontal Radius: Section of track that transitions from vertical to horizontal track welded, bolted or riveted to the horizontal track and then bolted to the flag angle

Horizontal Track: Track used in the horizontal segment of a track assembly

Hot Off The Floor: Condition where the door has a tendency to lift off the floor


Inside Hook Up: Connection where the counterbalance cable is on the inside of the track, between the door sections and the vertical track

Inside Hook Up Bottom Bracket: Bottom bracket where the cable is routed between the vertical track and the door section

Inside Lock: Spring loaded, sliding deadbolt lock or spring latch operable only from the interior of the door

Insulating Glass: Multi-pane glass assembly containing air space between panes for insulation

ISLO: Acronym for Inside Looking Out


Lift Handle: A handle attached to the inside or outside of a door section, to be grasped by hand when a door is to be operated manually


Meeting Rail: The top horizontal rail or bottom horizontal rail of any section that meets and joins to form a weatherproof seal

Mounting Plate: Flat steel or wood member placed on the wall to accommodate spring supports, spring shaft bearings, chain hoists and mounting plates for operators

Mullion Window: Framing member forming a divide between units of a window

Muntin: A bar member separating panes of glass within a sash or door


Opening Height: Distance from floor to the bottom of the header

Opening Width: Distance between jambs of the door opening

Operator: An electric or air-powered mechanism that opens and closes a door

Outside Hook Up: Connection where the counterbalance cable is on the outside of the tracks

Outside Hook Up Bottom Bracket: Bottom bracket where the cable is routed outside the tracks

Overlay: Decorative ornaments of metal, wood or hardboard used for outside decoration of garage door sections


Pan Door: A garage door composed of sheet metal door design sections

Perforated Angle: Angled metal with a serried of punched holes used to hang garage doors and operators

Perimeter Seal: Weatherstrip installed at the perimeter of a garage door

Pinch Resistant: Term for a door that has been designed to prevent entrapping, crushing, breaking, severing or dislocating a person’s finger


Rain Stop: Ledge provided at the point where the bottom rail meets the floor to prevent water from running under the door and allowing for runoff of the water onto the drive or approach

RSLO: Acronym for Right Side Looking Out

R-Value: Thermal resistance value; inverse of U-Value


Shaft Bearing: A bearing that is used to maintain torsion shaft alignment and reduce friction

S-Hook: Hardware device used to connect an extension spring to a pulley. These are also used with other door related hardware (i.e. chain on locks)

Sideroom: A horizontal measurement from each side of the door opening, outward to the nearest obstruction

Solar Glass: A type of tinted glass

Spring Anchor: Winding cone and stationary cone

Spring Balance: The amount of turns needed to counterbalance the weight of the garage door upward travel to reduce shock and prevent pull down rope breakage. Cane be made from leaf springs or tension rods

Spring Pad: Pad installed on header above the door to anchor the center bearing bracket. Can be mounted in various locations, not necessarily in center, depending on the size of springs

Step/Lift Plate: A part that can be used as a step down plate and a lift handle for manually operating a sectional door

Stile: Vertical reinforcement member of a section

Stile-and-Rail Garage Door: A sectional garage door featuring sections each made up of horizontal rail and vertical stile structural framing members that support panels connected to such members

Stop Mould: Serves to seal the perimeter of the door against weather and light infiltration; usually nailed to the jamb, outside the door

Strut: Support stiffener to reduce deflection of the door sections in horizontal position. Also, to increase wind load capability of door


Test Wind Load: Specified difference in static air pressure (positive or negative), equal to a specified percentage greater than or equal to 100% of the design load

Thermal Break: The separation between the outer and inner surfaces of a door section

Top Fixture: A bracket for positioning the top guide roller on the top section of the door

Top Seal: Weather stripping which fastens to the top of the door to seal the door along the top of the opening

Torsion Shaft: A shaft that transfers torque from springs to load

Torsion Spring: A spring that works by turning on end about a longitudinal axis, while the other end is held or turned in the opposite direction developing torque

Track Bracket: A fixture, connected to a track, which is designed for the track to be mounted to the jamb

Track Roller: Roller assembly for guiding the door sections along track

Trim: The finishing materials; such as the lock and handles on the door


U-Bar: See strut

U-Value: Thermal transmission coefficient which is a measurement of heat, in BTU’s, transmitted through one square foot of material (the door) in one hour at a temperature difference of 1 degree from one side to the other


Vertical Post: A vertical reinforcement sometimes installed for high wind events

Vertical Track: The portion of track that is oriented vertically and is adjacent to the jamb

Vision Lite: Glazing that is mounted in a door


Weatherstrip: Material used at the perimeter of a garage door, or between joints of a garage door, intended to improve a door’s performance against air infiltration and thermal transmission

Winding Cone: Part that fits into a torsion spring permitting winding and tension adjustment

Winding Plug Set Screw: Set screw fasteners used to lock the winding plug to the torsion shaft

Winding Rod: A solid rod that fits into the socket of the winding plug to tension torsion springs

Winds on Spring: The number of winding turns on a torsion spring

Wire Size: The diameter of the wire in a spring

Wood Jamb: Upright wood piece forming the side of an opening

Wood Jamb Mounted: Refers to mounting vertical track to wood jambs