Automotive Design Terms

Hey there core77 forum crew. Since we tend to like to talk about cars a lot, I thought iy might be helpful to share some common automotive design terms to help conversations. I pulled this list from the following two links:

My notes in parenthesis.


One-Box form
A categorization based on overall form design using rough rectangle volumes. In the case of the One-Box, also called a monospace or monovolume,[1] it is a single continuous volume. Slight wedge formed front or rear are still generally placed in this category. e.g., Bus, original Ford Econoline. The equivalent French term is volume, which you will sometimes see used by the British: “1-volume form”.
Two-box form
A categorization based on overall form design using rough rectangle volumes. In the case of the Two-box form, there is usually a “box” representing a separate volume from the a-pillar forward and second box making up the rest. e.g., Station Wagon, Shooting-brake, Scion xB (2006) The equivalent French term is volume, which you will sometimes see used by the British: “2-volume form”.
Three-box form
A categorization based on overall form design using rough rectangle volumes. In the case of the Three-box form, there is a “box” delineating a separate volume from the a-pillar forward, a second box comprising the passenger volume, and third box comprising the trunk area — e.g., a Sedan. The equivalent French term is volume, which you will sometimes see used by the British: “3-volume form”.


The line running over the car, from headlight to taillight, tracing the car’s silhouette. (basically the centerline)


The rear lamp. (I think this usually refers to the entire assembly)
A demarcation or crease between a vehicles body panels and the side windows.
Batsman’s crease
A tangent break feature line running along the centreline of a car. This kind of feature can be seen on many modern Vauxhall, Opel and Chrysler models. Literally derived from the break found on the rear side of a cricket bat.
The trim or bodywork that surrounds a light, holds the face of an instrument in position, or decoratively conceals gaps between bodywork and components as an escutcheon. Often chrome or plastic
The housing for the instrument cluster on top of or as part of the dashboard (also, don’t say dashboard, say IP).
The hood of the vehicle.
The trunk or liftgate of the vehicle.
Anything reflective added to a car to enhance appearance. May also be called chrome.
Body in White. Base chassis before customisation.
Butterfly doors
A type of door sometimes seen on high-performance cars. They are similar to scissor doors. While scissor doors move straight up via hinge points at the bottom of the A-pillar, butterfly doors move up and out via hinges along the A-pillar


Short for cabin. The enclosed compartment of a vehicle which contains the driver and passengers.
Cab back
The cab of the vehicle is moved to the rear of the vehicle. Cars such as a 1970s Corvette could be considered cab back design.
Cab forward
The cab of the vehicle is pushed forward. This design aesthetic was popular with Chrysler in the 1990s with the introduction of their LH platform cars.
Bodywork of a vehicle. Also the workshop at which automotive body work is built on a prototype or low volume production basis, typically with extensive handwork.
Character line
A line creased into the side of a car to give it visual interest. (interchangeable with swage line) Sometimes implemented by a rubbing strip.
Brightwork using chrome plating.
Material (usually plastic) added to exterior of the car which isn’t structurally necessary. May be functional to keep out dirt/debris as in underbody cladding, or may be cosmetic.
Control panel
Generally used in a car or truck for heating and cooling inside car environment according to the passenger requirements. Basically it is divided into different modes, blower speed functions, AC, temperature, and fresh recirculation of air. Worldwide control panel manufacturers are BHTC, Delphi, Visteon, Valeo, etc.
The base of the windshield.


Daylight Opening (DLO)
US DOT Term: For openings on the side of the vehicle, other than a door opening, the locus of all points where a horizontal line, perpendicular to the vehicle longitudinal centerline, is tangent to the periphery of the opening.
Daytime Running Lamp (DRL)
A daytime running lamp (DRL, also daytime running light) is an automotive lighting and bicycle lighting device on the front of a roadgoing motor vehicle or bicycle, automatically switched on when the vehicle is in drive, emitting white, yellow, or amber light. Their job isn’t to help the driver see the road but to help other road users see the vehicle.
Dash-to-Axle (ratio)
The critical relationship between front wheel centers and the windshield base. The most notable differences can be seen between cars with front-engine, front-wheel drive layout and front mid-engine, rear-wheel drive layout: the former tend to have longer front overhangs with a smaller dash-to-axle ratios, while the latter have shorter front overhangs with much greater dash-to-axle. Most so called premium vehicles (equipped with rear wheel drive) feature a relatively long dash-to-axle ratio.
The horizontal surface at the rear of the car, which usually serves as the trunk lid.
Dog leg
The area behind the rear door on a four-door car. This area is part of the quarter panel just behind the door and in front of the rear wheel house.
Down the Road Graphics (DRG)
The styling of the front end of the car, which people will instantly recognize and associate with a manufacturer. For example, the grille, lights and sometimes the DLO.


An external structure added to increase streamlining, deflect wind, and reduce drag.
The body-skin panel at the front of the car.
A car body style whose roofline slopes continuously down at the back found on cars with a single convex curve from the top to the rear bumper.
Fender (wings, UK)
Term for cowl covering the wheels of the vehicles. In more modern automobiles, this refers generally to the body panel or panels starting at the front “bumper” to the first door line excluding the engine hood. The opposite of the fender is the “quarter panel”.
A design used in older (pre-unibody) cars, trucks, and SUVs. The power train and body are mounted to a rigid structural framework called a rail. (also called a ladder frame)


A vent on the side of the fender that can be used as hot-air outlet, but usually decorative.
The glassed-in upper section of the car’s body. Daylight Opening (DLO) in turn describes the actual window areas only.
Gull-wing door
Car doors that are hinged at the roof rather than the side, as pioneered by the 1952 Mercedes-Benz 300SL race car. Opening upwards, the doors evoke the image of a seagull’s wings.


(1) The structural roof beam above the windshield. (2) The section of exhaust piping attached to the cylinder head.
Hofmeister kink
BMW’s trademark reverse-sweep kick at the bottom of last roof pillar.
H-point (or HP (Hip Point))
The pivot point between the torso and upper leg portions of the body, either relative to the floor of the vehicle[1] or relative to the height above pavement level, as used in vehicle design.
Hood (Bonnet in English speaking countries outside North America with the exception of the Canadian Maritimes)
The engine cover on vehicles when the engine is located forward or aft of the passenger compartment.
Heater, ventilation and air condition. A major package constraint both technically as well in interior design.


Instrument Panel. The dashboard is termed the instrument panel in the automotive industry. Sometimes this term is confused with the instrument cluster, the group of speedometer, odometer and similar devices generally behind the steering wheel.


A car body style that calls for a body with smooth contours that continues to a tail that is abruptly cut.


Plastic clips onto the base of the windscreen under the bonnet to protect from leaves and flowers.
Leafscreen retainer
Bonded to the base of the windscreen to provide a mounting surface for the leafscreen


NACA duct
A distinctively shaped inlet that is flush and begins with a narrow, shallow inset and becomes progressively wider and deeper. The duct was developed to introduce cooling air into aircraft engine nacelles, while increasing the drag of the nacelle only minimally. The duct was developed at the National Advisory Committee for Aeronautics (NACA).


The distance the car’s body extends beyond the wheelbase at the front (front overhang) and rear (rear overhang). In car style design terms, this is the amount of body that is beyond the wheels or wheel arches.
Obscuration band
Black graphite printed onto the glass to hide unsightly areas and improve aesthetics.


An open vehicle, usually with 4 doors, with a removable and/or retractable cloth top and a windshield characterized by the lack of integrated glass side windows. Contemporary uses of this name do not always follow this original description or apply to an open vehicle.
A structural member that connects the roof to the body of the car. Pillars are usually notated from front to back alphabetically (e.g. the A-pillar joins the windshield to the frontmost side windows, the B-pillar is next to the front occupants’ heads, etc.).
US DOT Term: Means any structure, excluding glazing and the vertical portion of door window frames, but including accompanying molding, attached components such as safety belt anchorages and coat hooks, that (1) supports either a roof or any other structure (such as a roll-bar) above the driver’s head or (2) is located along a side edge of a window.
The area at the base of the windshield where the wipers are parked. Also refers to the main chamber in an intake manifold.
Pontoon styling
A 1930s–1960s design genre when distinct running boards and fully articulated fenders became less common and bodywork began to enclose the full width and uninterrupted length of a car in a markedly bulbous, slab-sided fashion.
All the components that generate power and deliver it to the tyres.


(or rear quarter panel) refers to the panel at the back sides starting at the rear edge of the rearmost doors, bordered by at top by the trunk (boot) lid and at bottom by the rear wheel arches ending at the rear bumper. This is the opposite of the fender.
Literally, the term originally referred to the rear quarter or the car’s length.


The first application of the term rake in vehicles was probably the tilting back of the windshield’s top.[citation needed] Nowadays rake refers to the angle between the overall vehicle and the horizontal axis of the ground. If the back is higher than the front, the vehicle is said to have positive rake; if the front is higher than the back, this is negative rake. In early hot rod and custom cars, positive rake was created by varying tire size, and/or by suspension modification. In today’s body design, positive rake is integral in some vehicles’ styling, e.g. Mercedes E350 sedan, circa 2012/13.
An open vehicle, usually with 2 doors, with a removable and/or retractable cloth top and a windshield characterized by the lack of integrated glass side windows. Contemporary uses of this name do not always follow this original description. A classical roadster is a two-seater with a long hood and a short back, which means the driver is sitting in the rear of the vehicle (close to the rear axle). Usually it is a rear-wheel-driven car.
The body section below the base of the door openings sometimes called the “rocker panels”, or “sills”.
Rocker rail
Body armor protecting the Rocker, found mostly in off-road vehicles. Term coined by engineers at MetalCloak.[citation needed]
Rubbing strip
Plastic/rubber line or moulding to prevent side-swiping along the doors.


Saab hockey stick
The hockey stick is an automotive design feature seen on nearly all Saab automobiles. It is a C-pillar curve from the base of the rear passenger window that resembles the shape of an ice hockey stick or the Nike swoosh symbol.
Scissor doors
(Lamborghini doors) are automobile doors that rotate vertically at a fixed hinge at the front of the door, rather than outward as with a conventional door.
Inset or protrusion that implies the intake of air. May be functional for cooling/ventilation or purely ornamental. Also Shaker scoop.
Scowling headlamps
Headlamps styled along a V-shape as viewed from the front, giving the impression of a scowl.
The part of the body on a convertible or roadster where the windscreen is mounted. The term is used primarily in the UK.
Once a vehicle designed to carry hunters and sportsmen; now a station wagon or vehicle combining features of a station wagon and a coupe.
Shoulder line
The line or “shoulder” formed by the meeting of top and side surfaces extending from hood/fender shoulder to boot-lid/quarter-panel shoulder. The strongest example of this feature can be found on more modern of Volvo Cars.
The body section below the base of the door openings sometimes called the “rocker panels”, or “rockers”.
Sill line
Imaginary line drawn following the bottom edge of the greenhouse glass.
Six line
A line extending from the C-pillar down and around the rear wheel well.
A convertible top which is made out of flexible materials like PVC or textile.
Side covers for wheel arches, hiding the wheel — usually rear only. Also called fender skirts.
A raised lip or wing which is used to ‘spoil’ unfavorable air movement across the body. Some designs are more functional than others.
Staggered wheel fitment
The front and rear wheels are different widths. On sporty rear-wheel-drive cars, the rear tires are usually wider than the front.
Crease in the sheet metal intended as a “speed line” styling feature. Exemplified in the doors of the Ferrari Testarossa.
Suicide door
Hinged doors, opening from the front of the car. If accidentally opened while driving at a high speed, such doors would be blown backward.
Swage line
Crease or curvature in the side of the body used to create visual distinction. Sometimes the crease is functional and improves rigidity of the outer body (interchangeable with character line).
Swedish kiss
A negative flick-out to a flat surface which frames trim sections or venting.
Also called quarter glass; fixed glass located in between the side-door and boot.


The distance across the car between the base of the left and right wheels (like wheelbase, but side-to-side).
A typically large vehicle built using frame-on-rail construction consisting of a cab and a separate bed for cargo.
(Boot in UK) Compartment for storage of cargo which is separate from the cab.
Tube Fender
Replacement fenders found on off-road vehicles designed as part of body armor for off-road vehicles. Used to protect the thin sheet metal bodies from damage while off-roading.
Generally refers to the way the sides of a car rounds inward toward the roof, specifically of the greenhouse above the beltline. This term is borrowed from nautical description of naval vessels.
Turn under
The shape of the rocker panel as it curves inward at the lower edge.


Shape of the car as seen in the side profile. May be positive, negative or neutral. If the front is lower than the rear, then it is wedge-positive. If the rear is lower it is wedge-negative. If the car appears level from front to rear, then it is wedge neutral.
Wheel arch
The visible opening in the side of a car allowing access to the wheel.
Wheel arch gap
The space between the tire and the wheel well. Currently there is a trend towards smaller wheel arch gaps. Sometimes referred to as Dead Cat Space due to the fact that, in winter, many domestic cats try to seek shelter in wheel wells of recently parked cars in an attempt to stay warm.
The distance front to back measured from where the front and rear wheels meet the ground.
Wheel well (also wheelhouse, wheelhousing, or bucket)
The enclosure or space for the wheel.
Windshield trim
US DOT Term: Molding of any material between the windshield glazing and the exterior roof surface, including material that covers a part of either the windshield glazing or exterior roof surface.

anything missing?

Yes. Missing ‘truck nutz’ and ‘mud flaps’.

Seriously though this is a great list. Keep it sticky’d to the top.

Also an illustration describing the D2A ratio would be really useful especially as we now see electric vehicles that do not need to adhere to these ‘conventions’.

good call, I just switched it to a sticky post.

I always called the ‘leafscreen’ a wiper cowl.

This has always been one of the most helpful list on the internet - great to see it here.
I can check H-point for more terms when I find the time.

It will be helpful to add a few types of suspension in there too, as sometimes these influence the design and are visible; the double wishbone, the MacPherson strut, linear shock absorbers…

From what I can see the Cowl Panel is not in there, or whatever it’s called in English - the fireproof panel that the feet of the driver would hit when extending the legs fully forward, separating and protecting the occupants from the engine compartment.

I’m also not seeing the Diffuser. Or different types of aerodynamic diffusers we know from the automotive aftermarkets, but also integrated as a standard more and more.

Also the bulk often added above the rear wheels, like in the Juke, does that have a term? We always called it the Hip.
In older supercars such as the Testarossa, the hip would always flow nicely around the DLO into the trunk, adding to that low look. I miss that :slight_smile:
In trucks it’s Stepside vs. Fleetside.

Also I suppose we’re not going to add Moondisks just because I like them and to have anything under ‘M.’

Also the Aero Cover for the rear wheels, and other aero-mods aren’t in there yet.

From H-Point:

Backlight according to this book refers to the rear window, not the rear lamp.


Openings in the body structure i.e. the doors, trunk, movable glazing, and hood. Also called closures.

Box Sections
Load-bearing elements in the body assembly that help to form a strong, light weight structure.

Underbody structure including suspension, steering, brakes, fuel tank etc. Since the introduction of unit body construction used more and more to refer to the mechanical components only.

Cross Members
Beams that run across the body structure.

Curb Weight
Mass of a vehicle including all fluids with no occupants or cargo.

Datum (Planes, Lines and Points)
Used for reference during the design and build process. Very important theoretical elements that feature extensively in the package. For more information on GD&T including the use of Datums see my Formlabs article:

Final Drive
Drive shafts and differential assembly that transfer power from the transmission to the wheels.

Fire Wall
Bulkhead between interior and engine compartment, separating the passengers from heat generated by the engine and possible fire. For most front-engined cars, this panel is in front of the feet and is called the dash and footwell.
(this is what I meant earlier with Cowl Panel)

Hard Points
Theoretical points in space that represent parts of system envelopes. Set up by the engineering team for the designers to create the CAD or clay models over.

Happens to verify that cars meet local vehicle type approval for safety and emissions.

Upward suspension travel. Full jounce means fully compressed.

Knee Blockers
Area in instrument panel that prevents knees from sliding forward off the seat during frontal collisions.

Vehicle structure in which the chassis is integral with the body. Also called Unibody or Unit-Body. Typically made from pressed steel or aluminum sheets rigid enough not to require a separate chassis frame. Mechanical components are attached to subframes (cradles) or directly to the monocoque.

P1 & P2 Curves
Represent opening of the side door aperture panels. Usually the ‘heel and toe’ of the weld flange which the seals are mounted to.

Package / Packaging
All elements in the vehicle architecture driven by function, not style.

Beams that run longitudinally in the body structure.

Reach Zones
Theoretical surfaces that represent the limits of where the driver’s hands will comfortably reach controls.

Downward suspension travel.

Tire Envelopes
Volumes calculated by chassis engineers to describe tire profile as it is translated by suspension travel and steering. Include build tolerancing, flex(compliance) and snow chains.

Also the word ‘Designer’ is defined in the book as ‘staff who develop the aesthetics,’ in case anyone wonders what on Earth we are for.

I think its the ‘firewall’…? Not sure.

@slippyfish thanks, yes, I found out as well

Some suggestions…

Bangle Butt
Stylistic feature at the back of the car where the shoulder line flows down whereas the transversal trailing edge of the trunk flows upwards, ending in a sharp angle. First devised by Chris Bangle at BMW.

Bustle Boot Line
Stylistic feature at the back of the car where the trunk seems to be attached to the car as a separate volume, as in Chris Bangle’s BMW7 series.

Flame Surfacing
Shapes inspired by the flow of flames, such as those from the burning of gas under pressure.

New Edge
Styling theme as first devised by Ford that combines intersecting arcs and other features, leading to taut surfaces with crisp edges creating surface tension by adding creases to soft aerodynamic shapes.

Low chassis, often not much higher than the floor and mostly seen in EVs, that integrates a vehicle’s entire packaging, giving rise to a versatile platform on which to mount various types of bodywork.

Hood with integrated bonnet, wing and headlight fixture.

Heavy but strong chassis on which to mount engine, gear box, suspension and steering. Body is separately bolted on top. Also known as Ladder Frame.

Box Frame
Frame built from a number of plate materials and extrusions. Mainly used for custom builds and in combination with adhesives.

Mask Angle
Angle of dominant plane through the grille compared to the vertical plane, seen from the side of the car.
Example of a high Mask Angle: Honda Civic Type-R 2015.

System of extrusions, tubes and stamped components on which the engine, gearbox, suspension and steering are mounted. Body panels are attached to complete the structure. Suited for sports cars and custom-builds.

Tube Frame
Frame built from tubes and other profiles to support the external skin.