Auto Glass Glossary
The short answer
- Damage terms describe shape and origin: bullseye, half moon, star, combination, floater, edge and stress crack. Shape plus location decides repairability.
- Repair terms describe the process: bridge, vacuum and pressure cycle, resin viscosity, UV cure, pit polish.
- Replacement terms describe the bond: pinch weld, frit, primer, urethane bead, safe drive away time.
- Standards terms tell you which rule applies: FMVSS 205 and 212 are federal, ANSI/SAE Z26.1 is the glazing standard behind them, the replacement standard covers installation and ROLAGS covers repair.
- Insurance terms decide who pays: comprehensive coverage, deductible, assignment of benefits, OEM versus OEE glass.
Auto glass borrows its vocabulary from four worlds: fracture shapes, adhesive chemistry, federal standards and insurance claims. These are the 74 terms you will hear from a shop, an adjuster or an inspector, in alphabetical order. To name your own damage rather than look up a word, start with the damage identifier.
Terms A to E
Damage names, calibration types and coverage basics. For the shapes in context, see windshield damage types.
| Term | Definition |
|---|---|
| Acuity zone | A common informal name for the driver's primary viewing area, the glass in the forward sight line, where repairs get extra scrutiny. |
| ADAS | Advanced driver assistance systems such as lane keeping and automatic braking. The forward camera looks through the windshield. |
| Aftermarket glass | Glass made outside the vehicle maker's supply chain. Quality ranges from equivalent to visibly poorer in optics and fit. |
| AGRSS | The auto glass replacement standard, administered through the Auto Glass Safety Council. It covers adhesive use, training and glass retention. |
| AGSC | The Auto Glass Safety Council, which administers the replacement standard and registers shops that agree to be audited against it. |
| ANSI/SAE Z26.1 | The safety glazing materials standard referenced by federal rules. It defines glazing categories such as AS-1. |
| AS-1 line | A mark near the top of the windshield. Tint is generally permitted above it and restricted below it, and the driver's primary viewing area lies below it. |
| Assignment of benefits | A signed document transferring your right to collect claim payment to the shop, which then bills the insurer directly. |
| Backglass | The rear window, usually tempered and often carrying the defroster grid and antenna elements. |
| Bead | The triangular ribbon of urethane extruded onto the pinch weld or glass. Its profile sets bond thickness. |
| Bridge | The repair tool that mounts on the glass with suction cups and holds the injector square over the break. |
| Bullseye | A cone shaped separation with a dark circular ring around the impact point. The break type that fills most cleanly. |
| Calibration, dynamic | Recalibration performed by driving at specified speeds on marked roads while a scan tool runs the learn routine. |
| Calibration, static | Recalibration performed in a bay with printed targets set at measured distances and heights on level floor. |
| Calibration, dual | A procedure requiring the static routine and then a dynamic drive. Both must complete successfully. |
| Cold knife | A hand tool with a hardened blade used to cut the old urethane bead from outside the vehicle. |
| Combination break | A bullseye or half moon that also has legs. Measure it across its widest extent, legs included. |
| Comprehensive coverage | The part of an auto policy that pays non collision losses. Glass claims settle here, not under collision. |
| Cowl | The plastic panel at the windshield base covering the wiper mechanism and air intake plenum. |
| Crack | A linear fracture with measurable length, judged by length, origin point and location rather than by area. |
| Dam | A foam or rubber strip that limits how far urethane spreads and helps hold bond thickness. |
| Decking | Setting the glass into the opening. A dry deck is a trial fit without adhesive, to confirm alignment. |
| Deductible | The amount you pay before comprehensive responds. Some states and endorsements waive it for glass. |
| Delamination | Loss of bond between a glass ply and the interlayer, seen as a milky patch. Not repairable. |
| DOT code | The marking required on safety glazing identifying the maker, alongside the AS designation and model number. |
| Edge crack | A crack starting within roughly two inches of the perimeter. Rarely repairable, since the bonded edge carries load. |
| Encapsulation | Trim molded onto the glass edge at manufacture, forming one part. Damaged encapsulation means replacing the glass. |
Terms F to L
The federal standards and the construction terms that explain why a windshield behaves as it does.
| Term | Definition |
|---|---|
| Fibre line | A very fine hairline crack out of a break, tight enough that only thin resin enters. |
| Floater crack | A crack beginning in the field of the glass that never touches the perimeter. Most often accepted for repair. |
| FMVSS 205 | The federal glazing standard. It governs which glazing may be used in each opening and requires the corner marking. |
| FMVSS 212 | The federal windshield mounting standard, requiring much of the perimeter to stay bonded in a barrier crash. |
| Frit | The black ceramic band baked around the glass perimeter, shielding the urethane from ultraviolet light and aiding bonding. |
| Full cut | Cutting the old urethane down to the pinch weld. Riskier than trimming to a thin base layer, since bare metal needs priming. |
| Gel pad | The optically clear pad coupling a rain or light sensor to the glass. Single use. |
| Glazing | The regulatory term for transparent material in vehicle openings: windshields, side glass, backglass and roof panels. |
| Half moon | A partial bullseye, a crescent shaped separation rather than a full ring. It repairs well. |
| HUD | Head-up display. A HUD windshield uses a wedge shaped interlayer so the projected image is not a doubled ghost. |
| Interlayer | The plastic layer bonded between the two glass plies. Acoustic, solar and HUD versions differ in composition. |
| IR coating | A thin metallic layer reflecting infrared to cut cabin heat. Coated glass carries an uncoated window for transponders. |
| Laminated glass | Two plies of glass bonded to an interlayer. It holds together when broken rather than falling apart. |
| Leg | A radial crack out of the impact point of a star break. Air trapped at its tip leaves a silvery line. |
| Lite | Trade term for a single sheet of glass. A windshield is two lites bonded to one interlayer. |
Terms M to R
Parts, sourcing and repair chemistry. For how these fit together, see ADAS calibration explained.
| Term | Definition |
|---|---|
| Mirror button | The metal or ceramic pad bonded inside the windshield carrying the mirror and often the camera bracket. |
| Mobile service | Repair or replacement at your home or workplace. Temperature, wind, dust and calibration needs set the limits. |
| Moulding | Trim covering the joint between glass and body. It may clip in, slide in or be bonded. |
| OEE | Original equipment equivalent: aftermarket glass built to the original specification and feature set, without the maker's branding. |
| OEM | Glass supplied through the vehicle maker with its logo and part number. Usually the costliest option. |
| Pinch weld | The flanged metal channel the glass bonds to. Its paint must stay intact, since corrosion causes leaks. |
| Pit | The small crater at the impact point where glass was knocked out. Stress cracks have none. |
| Pit polish | Light polishing of the cured pit filler flush with the surface, removing the edge that catches light. |
| Post-scan | A diagnostic scan run after the work, documenting that no fault codes remain and any calibration completed. |
| Pre-scan | A diagnostic scan run before the work, recording the modules present and the fault codes that already existed. |
| Primer | Blackened adhesion promoter for prepared glass or exposed metal. It must flash off before adhesive goes on. |
| PVB | Polyvinyl butyral, the standard interlayer. It bonds the plies, restrains occupants and blocks ultraviolet light. |
| Rain sensor | An optical sensor bonded inside the windshield, detecting water by how light reflects off the outer surface. |
| Resin | The ultraviolet curing acrylic used to fill a break. Cured, its refractive index is close to glass. |
| ROLAGS | The ANSI accredited repair standard for laminated automotive glass: what should be repaired, what should not, what must be disclosed. |
Terms S to Z
Adhesive, curing and the terms that decide when the car is safe to drive again. See safe drive away time.
| Term | Definition |
|---|---|
| Safe drive away time | The interval after installation before the urethane can hold the glass in a crash. It varies with product and weather. |
| Sailboat crack | Trade name for a crack whose origin carries a small angled break. Judged under crack rules, not chip rules. |
| Setting tool | A suction cup handle, setting bar or powered arm that places the glass in one accurate motion. |
| Short crack | A crack within the length shops generally accept for repair, commonly up to about six inches. |
| Solar glass | Glass that cuts transmitted heat through a tinted interlayer, a reflective coating, or both. |
| Star break | An impact point with radiating legs and no separation cone. The hardest common break to make invisible. |
| Stop drill | Drilling a small hole at a crack tip to blunt the stress concentration before injection. It leaves a visible mark, and done badly it creates a new stress riser. |
| Stress crack | A crack with no impact point, caused by thermal shock, body twist or installation pressure. Almost never repairable. |
| Tempered glass | Heat treated single ply glass that breaks into blunt granules. Used for most side and rear glass. Not repairable. |
| Third visor frit | The frit patch at the top center of the windshield between the visors, hiding sensor mounts. |
| Urethane | The moisture curing adhesive bonding glass to body. It is structural, supporting the roof and the passenger airbag. |
| UV cure | Curing injected resin with ultraviolet light, from a lamp or sunlight, turning it from liquid to solid. |
| Vacuum cycle | The injection phase drawing air out of the break. Alternating vacuum and pressure is what empties tight legs. |
| VIN | The 17 character vehicle identification number, used to identify the correct glass among many variants. |
| Viscosity | The thickness of a repair resin, in centipoise. Thin resin penetrates legs, thicker resin fills cavities and the pit. |
| Windshield acuity zone | The same informal name written out in full: the critical viewing area ahead of the driver. See acuity zone above. |
| Wiper park | The strip at the windshield base where the blades rest, heated with embedded wires on some vehicles. |
Which standard governs what
Four names get used interchangeably and should not be. FMVSS 205 governs the glazing itself, FMVSS 212 governs how the windshield stays in the opening during a crash, and both are federal. ANSI/SAE Z26.1 is the glazing materials standard behind FMVSS 205 and the source of the AS-1 glazing class, though not of the AS-1 line itself, which is a manufacturer convention state laws adopted. AGRSS is the industry consensus standard for replacement, administered through the AGSC, and ROLAGS is the ANSI accredited standard for repair.
The federal standards apply to the glass and the vehicle. The industry standards apply to whoever works on your car and are followed voluntarily, which is why a technician may decline to fill damage in your sight line even where the state would let you drive on it. See the AS-1 line and driver view and how chip repair works.
Frequently asked questions
What is the difference between OEM and OEE glass?
OEM glass is supplied through the vehicle maker and carries its logo and part number. OEE means original equipment equivalent: aftermarket glass built to the same specification and feature set without that branding. Fit and optical quality vary more across OEE brands.
What does safe drive away time actually measure?
It is the interval after installation before the urethane has developed enough strength for the glass to stay bonded in a crash. It is specific to the adhesive product and to temperature and humidity, so it is stated by the adhesive maker, not by the shop.
Is a star break the same as a combination break?
No. A star break is an impact point with radiating legs and no full separation cone. A combination break is a bullseye or half moon that also has legs. Combination breaks are the most common damage shops see and are measured across their widest extent.
What is the AS-1 line for?
It is a mark near the top of the windshield that manufacturers put there by convention, and state tint laws adopted it as a boundary: film is generally allowed above the line and restricted below it. ANSI/SAE Z26.1 is a different thing, the glazing standard that defines the AS-1 class of glass. The driver's primary viewing area sits below the line, not above it.