Retractable Awning and Screen Glossary: Terms Explained

The vocabulary of retractable awnings and screens, defined in plain English, with a link to the guide that explains each term in depth.

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Acrylic-coated fabric: Awning fabric with an added acrylic or fluorocarbon coating that raises water resistance while keeping some breathability. Learn more
Anemometer sensor: A wind sensor with spinning cups that measures wind speed at its mounting point and signals a motor to retract the awning above a set threshold. Learn more
Arm elbow: The hinge in the middle of a lateral arm. It contains the cable, belt or chain that transfers spring force across the joint. Learn more

Brush pile: A strip of dense fibers in a channel that seals the gap between a moving screen and its frame against insects and drafts. Learn more

Cassette: A closed aluminum housing that fully encloses the rolled fabric and folded arms when an awning is retracted, protecting them from weather and debris. Semi-cassettes cover only the top of the roll. Learn more
Crank handle and gearbox: The manual drive of a retractable awning: a removable handle that turns a worm gearbox at the end of the roller tube. Learn more

Drop arm awning: An awning with two arms that pivot from the bottom of the window or wall, swinging the fabric out and down at an angle. Common on windows and balconies. Learn more
Drop screen or drop valance: A second roll of screen fabric mounted in the front bar that lowers vertically to block low sun from the front of the awning. Learn more

EN 13561: The European standard for external blinds and awnings, covering performance and safety, including the wind resistance classes used to rate awnings. Learn more

Freestanding awning: A retractable awning supported by its own posts or frame rather than a building wall, often with an awning on one or both sides. Learn more
Front bar: The rigid aluminum profile at the outer edge of an awning. It holds the fabric hem and connects to the arm ends, and often carries the valance or drop screen. Learn more

Gas strut: A pressurized cylinder used in some drop arm and RV awnings to push arms outward. Uncommon in lateral arms, which mostly use coil springs. Learn more
GFCI: Ground-fault circuit interrupter: a protective device required for many outdoor outlets that cuts power on a current leak. A tripped GFCI is a common cause of a dead awning motor. Learn more

io-homecontrol: A two-way radio protocol used by Somfy and other makers. Motors confirm commands back to the controller, unlike one-way RTS. Learn more

Keder (welt): A bead sewn into the edge of fabric that slides into a matching groove in the roller tube or front bar to hold the fabric securely. Learn more

Lateral arm: A folding, spring-loaded arm that extends horizontally from the wall to push the awning out and keep the fabric taut without posts. Most retractable patio awnings use two or more. Learn more
Limit settings: The programmed stop points of a tubular motor for fully open and fully closed. Lost or drifting limits cause awnings to stop short or overrun. Learn more
Louvered roof: A fixed-frame pergola with rotating aluminum slats that open for light and close for shade and rain. Learn more

Manual override (CSI): A motor feature that allows the awning to be cranked by hand if the motor or power fails. Learn more
Mounting bracket: The steel or cast aluminum hardware that attaches the awning's torsion bar to the wall, soffit, fascia or roof. Learn more

NFPA 701: A US fire test standard for textiles. Commercial awnings and screens often need fabric that passes it. Learn more

Openness factor: The percentage of a screen fabric's area that is open weave. Lower openness blocks more sun and gives more daytime privacy; higher openness keeps more view and airflow. Learn more

Pergola awning: A retractable fabric roof that runs in side rails on a post-supported frame, so it can be fully supported at both ends. Learn more
Pitch: The angle of an extended awning below horizontal. More pitch sheds rain and blocks lower sun but lowers the front bar and reduces headroom. Learn more
Pleated screen: A screen whose mesh folds like an accordion instead of rolling. It stays where you leave it and suits wide or busy openings. Learn more
Projection: How far an awning extends out from the wall when fully open, measured along the arms. Actual shade is usually less than projection. Learn more
PTFE thread: A UV-proof sewing thread used for awning seams that typically outlasts the fabric, unlike standard polyester thread. Learn more

Roller tube: The tube that the fabric winds onto. In motorized awnings it houses the tubular motor. Learn more
RTS (Radio Technology Somfy): Somfy's one-way radio protocol for motors, remotes and sensors. Widely used, simple to pair, but motors cannot report their status back. Learn more

Semi-cassette: An awning with a hood that covers the top of the fabric roll but leaves the underside and arms partly exposed when closed. Learn more
SHGC: Solar heat gain coefficient: the share of solar heat a window lets in, from 0 to 1. It sets how much an awning can save. Learn more
Solar screen: A tightly woven exterior screen fabric (often PVC-coated polyester) that blocks much of the sun's heat and glare while preserving some view. Learn more
Solution-dyed acrylic: Acrylic fiber colored by adding pigment to the liquid polymer before it is spun, so color runs through the fiber. It resists fading far better than surface-dyed fabric. Learn more
Spline: The rubber or vinyl cord pressed into a frame channel to lock screen mesh in place. Sized by diameter. Learn more
Square bar: Another name for the torsion bar: the square steel or aluminum beam that carries the arms and brackets. Learn more
Sun sensor: A light sensor that extends an awning or screen when sunlight exceeds a set level and retracts it when it drops, usually paired with a wind function. Learn more

Torsion bar: The structural square bar running the width of the awning that carries the arm shoulders and connects to the wall brackets. It resists twisting under load. Learn more
Tubular motor: A motor and gearbox packaged in a tube that slides inside the roller tube. Rated by torque (Nm) and speed (rpm), with built-in limit switches. Learn more

UPF: Ultraviolet protection factor: a rating of how much UV radiation passes through a fabric. UPF 50 lets through about 1/50 (2%) of UV. Learn more

Valance: The strip of fabric hanging from the front bar. It adds a finished look and a little extra shade from low sun. Learn more
Vibration (motion) sensor: A wind sensor mounted on the front bar that detects the awning's own shaking and triggers retraction. Learn more

Waffling: Wavy lines in awning fabric near seams caused by extra thickness at the seam when rolled. Cosmetic, not a defect in most cases. Learn more
Wind class: A rating from 0 to 3 under EN 13561 describing the wind load an awning withstands in testing: roughly 17, 24 and 30 mph for classes 1, 2 and 3. Learn more

Zip-track: A screen system in which a zipper-like edge welded to the fabric runs inside the side channels, locking the screen against wind and sealing the edges. Learn more