Everyone Needs a Roadmap to the Terminology

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Garage Doors | Garage Door Openers

This comprehensive garage door glossary is very extensive, but may not be entirely complete when it comes to all garage and garage door terms that are often used when describing residential garage doors, garage door installation and garage door service.

Toledo Door and Window wants to give you a head start in better understanding your garage door. Simply click the letter below and it will take you directly to the terms that begin with that letter.



Support member used to fasten torsion spring assembly of a vertical lift door to the wall above the door opening.

Adjusting Cone (Winding Sleeve, Winding Cone)
Part that fits into torsion spring permitting winding and tension adjustment.

Air leakage rating
A measure of the rate of infiltration around a window or a skylight in the presence of a strong wind, expressed in units of cubic feet per minute per foot.

The space in the cavity between two panes of glass in an insulated glass unit.

Angle-Mounted Track
A method of fastening vertical track to a door jamb using a fully adjustable continuos angle.

An inert, nontoxic gas placed between glass panes in insulated windows in order to improve the insulating value of sealed glass units.

Weather-strip attached to the bottom of the door to seal it against the floor.

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The distance from the door opening into the building to the first obstruction at the required headroom.

Booster Spring
Additional spring provided to compensate for weakened counterbalance. (Usually extension spring.)

Bottom Fixture (Bottom Corner Bracket)
A structural support located on the bottom section, which hold track rollers and provide for attachment of the lifting cables on the sectional doors.

Bracket Mounted
Method of fastening vertical track to a doorjamb using jamb brackets.

An abbreviation for British thermal unit - a standard measure of the amount of energy required to raise one pound of water by one degree Fahrenheit.

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Cable Clamps
A manufactured device used to secure two pieces of cable to each other. Size of clamp is determined by the cable diameter.

Cable Drums
Grooved drums fitted on torsion spring shaft onto which lifting cable is wound when door is opened.

Cable Safety Device
A safety bottom fixture specifically designed to prevent a door from falling in the event of cable breakage.

Carry-Away Post
A lightweight extruded aluminum post/track assembly which substitutes for door jamb in multiple door installations where a clear span is required. Can be released and carried from opening.

Center Hinge
Flat hinge located on all intermediate stiles to allow for section break as door operates.

Center Lift Cable
An additional lifting cable attached to the exterior of the door to provide support for extra wide or heavy doors.

Center Stile/Stile/Mullion/ Mutt
Vertical members of a door section which provide structural rigidity and location for center hinge attachment.

Chain Hoist
Refers to sprocket or pocket wheel attached to shaft with chain operation giving varying mechanical advantage in various ratios.

The accumulation of water vapor or droplets as the result of warm, moist air coming in contact with a cold surface and cooling to its dew point temperature. Condensation may occur when a cold window glass or frame is exposed to humid indoor air. Low-conductivity, insulated glass and warm-edge spacers reduce condensation.

The transfer of heat through a solid material, such as glass or wood, through direct contact. Heat flows from a higher-temperature area to a lower-temperature one.

Contour Track
Special horizontal track with more than one radius used in specialty applications.

The flow of heat that occurs through a circulating gas or liquid (such as air) as warm air rises and cool air sinks. Convective heat transfer can take place in large areas (like rooms and buildings) and in small areas (like the cavity between two layers of insulated glass). Low-e insulated glass units lessen cold convection currents by maintaining warmer interior glass surface temperatures.

Corner Bracket
See Bottom Fixture.

Refers to design of door mechanisms using weights instead of springs to counterbalance door weight.

One full opening and closing operation of a sectional door.

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Door and Access System Manufacturing Association. International manufacturing trade association with 5 divisions: residential and commercial sectional doors; rolling doors; operator and electronics; specialty; and association division.

Dead Load
A static applied load. A load without movement.

Double Car (DC)
Door section width > 10' 1".

Double Low Headroom Track
Special horizontal track with a pair of tracks used to reduce the high point of travel of the top section of a door to permit installation in a low headroom application.

Double Shaft
Double torsion spring shaft used when additional space is required to accommodate counterbalance spring wire.

Duplex Spring
A combination of two torsion springs of different diameters telescoped within common spring plugs.

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Edge Hinge (Roller Hinge)
Graduated hinge, which is attached to end stile of the door sections to carry track rollers and allows for section breaks as a garage door operates.

Electric Interlock
Interlock to prevent door operation by electric motor under specific circumstances.

Electric Opener
Electric motorized device to control door cycling.

The relative ability of a surface to reflect or emit heat by radiation. Emissivity factors range from 0.00 to 1.00. The lower the emissivity, the less heat that is emitted through a window system. Emissivity is typically measured by U-factor (or its inverse, R-factor).

End Stile
Stile located at each end of a door section, which provides for attachment of edge hinges. These stiles carry the total section load and should be of superior strength to provide structural integrity.

A joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy helping us all save money and protect the environment through energy efficient products and practices. www.energystar.gov

ENERGY STAR® windows program
A voluntary partnership between the U.S. Department of Energy (DOE) and the fenestration industry to promote sales of energy-efficient windows, doors and skylights. The program establishes three climate regions with one recommended product designation for each region. All ENERGY STAR® windows must be NFRC-rated, certified and labeled for both U-factor and solar heat gain coefficient.

A label that indicates a window meets ENERGY STAR® program energy-efficiency requirements for a specific region, and is at least 40% more efficient than products required under the most common national building codes.

Extension Spring
Counterbalance springs, which provide lifting power by stretching. Generally mounted above horizontal tracks.

Exterior Lock
Keyed lock, which can be operated on exterior of the door.

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A window or skylight and its associated interior or exterior elements (e.g., shades or blinds).

A metal ring or cap that is affixed to a cable so as to form a bottom or loop on the end of the cable.

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Gas fill
An insulating gas (such as argon or krypton) placed between window glazing panes to reduce the U-factor by suppressing conduction and convection.

Garage Door Openers

Glass or plastic panes, as in a window or skylight. Note that the terms "double-glazed" and "double-paned" are interchangeable. (The term "glazed" should not be confused with "coated" or "tinted.")

Graduated Seal
Design of tapered vertical track and a graduated height of edge hinges, which assure a weathertight, fit between door and jamb.

Also called "muntins." The decorative bars that divide the glass part of a window up and create a pattern. Sunrise Windows grids are located between the panes of glass.

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The distance above the top of the door opening to the nearest obstruction.

Special plate attached to front of horizontal tracks for limited sideroom application.

Header Seal
Weather-stripping which fastens to the top of the door to seal the door along the top of the opening.

High Lift
See Lift Clearance.

High Cycle Springs
Special counterbalance springs with increased cycle lift capability for high usage doors.

Horizontal Track Assembly
An assembly made up of a piece of track and which can be reinforced with a piece of angle that is used to both guide and support the door in the horizontal position.

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IDA International Door Association
The dealer/installer trade association.

Inclined Track
A horizontal track that follows the slope or slant of a building roof line.

The inadvertent flow of air into a building through breaks in the exterior surfaces of the building (e.g., through joints and cracks around window and skylight frames, sashes and glazings).

Inside Lock
Spring loaded, sliding deadbolt lock operated only from interior of the door.

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Jackshaft Opener
Electric operator which mounts on the wall or ceiling and directly drives torsion spring shaft.

Jamb Angle (Jamb Bracket)
"L" shaped bracket used to fasten vertical tracks to doorjambs.

Jamb Seal
Weather-stripping attached to doorjambs to help seal door along the jambs.

Joint Seal
Weather-stripping attached to door section meeting edges to seal door between sections.

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Laminated Glass
An insulated glass unit in which one internal piece of glass is covered (laminated) with an organic film. The film gives the glass an added degree of resistance to breakage.

Lap Jamb
Condition where door sections lap the door opening one inch on each jamb.

Lateral Force
A force applied from or toward the side.

Lift Clearance
The distance above the top of the door opening to the centerline of the horizontal track. This term is often confused with the term "headroom."

Term for windows in sectional doors.

A section of glass. This term can be confusing, as it can refer to an entire window (as in a 4-lite bow) or to one of the areas of glass divided up by muntins/grids/grilles. Sunrise uses the term "lite" only to refer to bow windows, which can come in 4-lite, 5-lite, or 6-lite sizes.

Low-emissivity (low-e) coating
Microscopically thin, virtually invisible metal or metallic oxide layers deposited on a window glazing surface and sealed in an insulating glass unit to reduce the U-factor by suppressing radiative heat-flow through the window.

Low Headroom
Hardware accessories to provide for door installation with minimum headroom conditions. Usually less than 16" headroom.

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Metallurgist Report
A report of document that describes the composition of a material.

Mill Certification
A report or document from the producing mill that provides all pertinent data relative to the composition, structure, heat, etc. of a given material.

A slender dividing bar fixed or removable between two doors. Usually designed to carry wind load and not vertical load.

Also called "grids" or "grilles." The decorative bars that divide the glass part of a window up and create a pattern. Sunrise Windows muntins are located between the panes of glass.

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National Fenestration Rating Council - a nonprofit public/private collaboration that provides contractors and homeowners with a standardized energy-performance rating system for fenestration products; administers independent rating and labeling system for energy performance of windows, doors, skylights, and other attachment products. www.nfrc.org

Normal Headroom
Hardware standard to provide for door installation with standard headroom conditions. Usually 16" to 24" of headroom.

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One Piece Door
Also known as Shin-busters. A door that operates as one-piece, rather than a door made of mutliple sections.

Open Back Door
Hollow door with no insulation or back.

Area of the garage exterior where a garage door will hang for closure.

Opening Height
Distance from garage floor to the top of an opening.

Opening Width
Distance between left and right jambs of an opening.

Opener / Operator
A device used to control the up and down motion of a door.

Outside Hook-Up
Bottom fixture with an arm that bends around vertical track to receive lifting cables. Generally used with low headroom hardware.

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The area between stiles in a door section. The "look" of a door is considered the "panel style."

Pass Door
Entry person door which is built-in to a sectional door.

Passive Solar Heat Gain
Solar heat that passes through a material and is captured naturally, not by mechanical means.

Perimeter Seal
Complete weatherstripping package for sectional doors consisting of astragal, jamb seal and header seal.

Pocket Wheel
A wheel or drum machined in a way to receive the individual links of a chain. Used to transmit direct power.

Push Down Spring Bumper
Spring-activated push rods mounted on horizontal tracks to force door down during closing portion of door cycle. Generally used with jackshaft type operator or manual chain hoist with standard lift.

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Radial Force
A force generated from the center of an object toward the outside.

The transfer of heat in the form of electromagnetic waves from one surface to another.

Relative Heat Gain (RHG)
A calculated relationship of heat gain (through a window system) that accounts for center-of-glass U-value and center-of-glass shading coefficient based on a standard inside and outside temperature.

Steel and nylon, usually with ball-bearing wheels that allow sections to roll freely along door tracks.

R-value is a measurement of thermal efficiency of a garage door, or how well the garage door insulates. The higher the R-value, the increased thermal efficiency of a garage door. Be aware that manufacturer’s R-value calculations may vary. To compare R-value, make sure manufacturers follow the DASMA (Door and Access Systems Manufacturers Association) guidelines by stating Calculated door section R-value is in accordance with DASMA TDS-163. ; A measure of a product's ability to resist the transfer of thermal energy. The inverse of U-factor (R=1/U), R-value is expressed in units of hr-sq. ft -ºF/BTU. A high R-value window has greater resistance to heat-flow and a higher insulating value than one with a low R-value.

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Sandwich Door
Triple-Layer: Steel + Insulation + Steel Interior. Classica 3000, Heritage 3000, Stratford 3000 and Olympus (residential) and Models 2700, 1380, 1350, and 1000 (commercial).

A substance, which adheres to the glass and the spacer, sealing an insulated unit. It must provide adhesiveness and a minimum of moisture transmission through itself. When one substance provides both these characteristics adequately, the unit is called a single-seal unit. Sometimes two materials are needed for the desired result, which makes a dual-seal unit.

Individual components of a garage door. Garage doors are made up of multiple sections to fill the appropriate height of a garage opening. 7' tall doors are typically comprised of 4 sections spanning the width of an opening. 7' tall doors in the Amarr Classica Collection are made with 3 sections to provide a more vertical, authentic carriage house door look.

Shading Coefficient (SC)
A measure of the ability of a window or skylight to transmit solar heat, relative to that ability for 1/8-inch clear, double-strength single glass. This measurement is being phased out in favor of solar heat gain coefficient, and is approximately equal to the SHGC (see below for definition) multiplied by 1.15.

Shaft Bearings
A free rolling, cylindrical, ball bearing that is used to guide the torsion shaft, maintain alignment, and reduce friction.

A pulley with a ball bearing built into it that is designed to handle a cable and used to control the movement of the cables employed in door counter balance system.

SHGC (Solar Heat Gain Coefficient) is a measurement of how much of the sun's heat is transmitted through the window or door. It is best described in terms of a ratio; where 1 is the maximum solar heat gain that comes through a window and 0 is the minimum. A window that has a SHGC of .3 will allow 30 percent of the sun's heat to pass through. Whether you want a higher or lower number will depend on your goal. A product with a low SHGC will help to block heat and reduce cooling loads in hot weather; a product with a high SHGC will be more effective at harnessing solar heat in cold weather.

Side Bearing Plate (End Bearing Plate)
A bracket that attaches to the horizontal supports and possibly the wall to provide a bearing surface for the torsion shaft near the ends.

Distance from each doorjamb to the nearest obstruction.

Single Car (SC)
Door section width < 10'

Solar Heat Gain Coefficient (SHGC)
The fraction of solar radiation transmitted through a window or skylight, expressed as a percentage. The lower a window's SHGC, the less solar heat it transmits and the greater its shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly. Generally, a lower SHGC is desirable in warm climates, and a higher SHGC is desirable cold ones. SHGC has replaced shading coefficient (SC) as the standard indicator of a window's shading ability.

Solar reflectance
The measured quantity of energy in the solar wavelength range that is reflected by a window, expressed as a percentage.

Solar transmittance
The measured quantity of energy in the solar wavelength range that passes through a window, expressed as a percentage.

A material placed between two or more panes of glass in an insulated glass unit to bond and seal the glazing unit.

Spring Assembly
Hardware used to make up door counter-balance assembly.

Spring Bumper
Small spring-cushioned bumper attached to horizontal track to stop door at full open position.

Spring Pad (Center Bearing Plate)
Plate or bracket which is located on the wall above door opening to receive torsion spring assembly support brackets.

Spring Fittings
The sleeves or cones that are used to adapt the torsion springs to the torsion shaft. Torsion springs usually have two fittings or cones. One is a stationary sleeve or spring retainer, while the second piece is an adjusting cone or winding sleeve.

Stationary Sleeves (Spring Retainers)
Part that fits into the end of a torsion spring permitting the spring to be anchored to the spring anchor plate.

Steel Gauge
Steel gauge is the thickness of the steel material used in garage doors. The lower the steel gauge number the thicker the steel. Real steel gauge is the true thickness of the steel material. Nominal steel gauge is the average thickness of the steel material used in production due to a plus/minus tolerance level. Real steel gauge is the minimum gauge of steel material used in production.

Vertical members of a door section which provide structural rigidity and a location for hinge attachment. Generic term.

Support stiffener used to increase wind load capacities of a door, as well as reduce deflection of a door section in the horizontal position.

Swing-Up Post
An extruded aluminum post which substitutes for doorjambs in multiple door installations where a clear span is required. Operated by a hand winch or electric operator, it swings up parallel to header.

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Tapered Vertical Track
Refers to the graduated spacing of the vertical track away from the jamb permitting weather-tight closing of door against jamb.

Tempered Glass
Special heat-treated, high-strength safety glass which shatters into pebble-sized particles and not in slivers.

An ultra-hard metal with low light absorption and high visible light transmittance (VLT) properties. Used in Sunrise’s Ultra-U+Plus Glass, titanium low-e coatings improve transmitted color and reduce emissivity.

Top Fixture
Adjustable brackets, which usually carry track rollers, mounted on the top corners of the top section of the sectional door.

Torsion Shaft
The shaft of a torsion spring assembly, which transmits lifting power of the torsion springs to cable drums and lifting cables.

Torsion Springs
Counterbalance springs which provide balancing power by winding and unwinding through door cycle.

Channel shaped metal bars that guide rollers on sectional garage doors.

The arc of travel or sweep of the top section as the door is raised from closed to open position.

Trolley Operator
Electric operator, which mounts above the door in the horizontal position and lifts door by pulling, and pushing the top section. Specifically designed for normal headroom and low headroom doors.

Truss (Struts)
Support stiffener used to increase wind load capacities of a door as well as reduce deflection of the door sections in the horizontal position.

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U-factor (U-value)
A measure of the rate of non-solar heat-flow through a material or assembly. It is expressed in units of BTU/hr.-sq. ft. -ºF (or W/sq. m-ºC), and may be expressed for the glass alone or for the entire window assembly, including frame and spacer materials. The lower the U-factor, the greater a window's resistance to heat-flow and the better its insulating value.; the measurement used in determining the ability of different structural components (such as windows) to conduct heat. U-factor can tell you how well windows will hold in heated or cooled air. The lower the number is, the better.

Upper Vertical Track
Horizontal track assembly on a vertical lift door.

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Vertical Lift
Refers to a hardware design that causes doors to open vertically, no horizontal tracks required. This hardware is normally operated with spring counterbalance, but also possible with weight counterbalance.

Vertical Track
Track assembly mounted to door opening jambs to guide and support a sectional door in the "closed" or "vertical" position.

Visible light transmittance (VLT or VT)
The percentage or fraction of the visible light spectrum that is transmitted through the glass of a window or skylight as reduced by the sash material and reflectance of the glass.

Visible reflectance
The measured amount of energy in the visible wavelength range that is reflected by a window system, expressed as a percentage.

Visible Transmittance is the percentage of the visible light transmitted through a particular piece of glass. Visible light is the part of the solar energy spectrum that we can see.

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Describes a window unit that uses a new spacer material (e.g., rubber or stainless steel or plastic vs. aluminum) and/or a thermal-break spacer design to reduce conductivity between interior and exterior glass panes.

Wind Load
The amount of force (in PSF) exerted by the wind along the face of the door as it stands in the opening. Click here to learn more about Amarr's Wind Load doors.

Winding Sleeve (Adjusting Cone)
Part that fits into torsion spring permitting winding and tension adjustment.

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