Five weird car design terms, explained

Every professional field has its own jargon, and car design is no different. Here are five of the most curious terms from an automobile designer’s vocabulary, “translated” into plain English.

Author’s illustration of the Citroën DS

DLO or Daylight Opening

DLO or Daylight Opening (Illustration from the Author)

Nothing beats a well-placed acronym to sound smarter than your peers in a meeting, and DLO, or Daylight Opening, is perhaps the most egregious example. The term likely originated from architecture, but car designers today use it to describe the glass area on a vehicle’s bodyside, between the first and the last roof pillar. A widespread visual trick is to finish one or more roof pillars in black to visually connect the glass panes, making the “DLO” look larger than it is.

A, B, and C pillars

The alphabetical “names” of roof support structures (Illustration from the Author)

The pillars that support the roof are identified in alphabetical order, starting from “A” for the ones besides the front windscreen, then “B” for the pillars behind the front doors, and “C” for the rearmost ones. Station wagons, minivans, and SUVs also have “D” pillars as their roof stretches further back, needing more structural support.

Beltline

The “beltline”, visualized (Illustration from the Author)

The “beltline” is an ideal line that connects the side windows’ base, and it’s a key graphic element in car design.

Shoulder

Yes, cars have “shoulders” too. (Illustration from the Author)

Car designers have applied quite a few anatomical terms to vehicle parts, but “shoulder” is perhaps the weirdest, as it’s located below the “beltline”!
Except for minivans or small cars…