Crown in a panel is compound curvature - usually convex: in one plane it would simply be 'curvature'.  To the engineer, crown provides inherent stiffness; to the designer it enables the control of highlights and lightlines.

The appearance of flatness can be achieved and accurately controlled by the use of gentle crown, but true flatness can't.

A simple way of 'measuring' crown is to compare it with an offered-up straight-edge.  There is always considerably more crown - in any direction - on automotive surfaces than seems apparent, likely, or even possible.

Glass is not considered to have crown.  Glass surfaces, particularly windscreens, are to all intents and purposes, single curvature: the principal curvature - in plan for front and rear screens, end elevation for side glass - dominates any slight, but necessary curvature in the opposing planes. 

The expression derives from 'Day Light Opening' and is used to describe the graphic shape of a car's side glass. The DLO is the strongest and most important graphic element of a car's design, as it provides the opportunity to create a major contrasting surface which can be employed to flatter or accentuate a form. 

Where there's graphic continuity, it may also include the front and/or rear screens.  This notion has really only been convincingly achievable since the advent of flush glazing and bonded front and rear screens which additionally enabled non-opening pillars to be glazed over (illus. Mini)

The desired effects work best with lighter colours which contrast strongly with relatively dark tinted glass, blacked-out pillars, cheater panels and internal window 'masking'.  (This is the reason most cars are designed in silver) To add further emphasis - or to add some in the case of dark-colored cars - the DLO may be 'outlined' with a bright strip.

The design features and characteristics of the front end or 'face' of a car which enable the marque to be immediately identified from a distance.

By joining up the dots, Audi's initially controversial new face banished the anonymity of the dull letterbox grille, and made them identifiable a mile away. 

Reduced ground clearance, fatter tyres and extended wheelarches are readily spotted performance signifiers which introduce the similarly distance-related notion of 'down-the-road dynamic'.

A thin, pre-painted stretchable plastic film made by 3M that is applied rather like a transfer by sliding it into place off its wetted backing paper. 

In a normal clay model, door and other shut lines, wheels and other areas of contrast will be added, leaving the bare clay to represent the painted surfaces.  This provides effective 3-D graphic contrast, and a representation, which those with a trained eye find rather pleasing. 

However, the subtleties and finer nuances of the design may still effectively be 'camouflaged' by the non-reflective clay, so the next step will be to Di-Noc or paint - usually in silver - the remaining surfaces.  The advantage Di-Noc has over paint, is that it can be simply peeled off to facilitate design changes - paint has to be scraped off, damaging even those surfaces which don't require change.

A simple line in a car's body surface. The best feature lines will be sympathetic to the design of a car, but some may simply have been introduced to relieve otherwise dull or large areas of 'plain' sheet metal.

They can also be used to accentuate the form, and to link, tie-in, co-ordinate or visually organise the loose array of items such as door handles, vents, rear number plate recess, front and rear lenses etc which appear on all cars.

Any and all body panels may have feature lines - some have been known to have too many. 

See also crease line

Fenders are those local panels which are legally required to wrap or cover road wheels, protecting the bodywork - sometimes the occupants - and other road users from spray, dirt, stones and anything else thrown up by the revolving tyres.  

In their early, simplest form, they closely followed the shape of the wheel, like bicycle mudguards - hence the name 'cycle wings'.  The front ones particularly were quite separate from the body and often turned with the wheels.  Today, identifiable front fenders live on in all body configurations, but rear fenders only in three-box saloons: in hatchbacks, the panel which accommodates the rear wheel is referred to as the rear quarter panel.

Some vehicles, such as Jeep (pictured right), still retain identifiable fenders but in most cars they have become integrated in the overall body. There is a fashion for fenders to become more prominent again, in a bid to suggest power or for a better stance (illus. Chevrolet Volt).

Cheap, light and easily-replaceable plastic front fenders are 'discretely' used on a number of cars - the Mercedes A-Class for example. Renault has used plastic front fenders on many models for years.

UK English: Wing