What is it?

[BazaJT]

So in a few spare moments I was scanning a brochure with an article about the Fiesta/Focus/Mondeo ST-Line range[not that I'm going to be buying one!]There was a list of bits that make an ST-Line what it is,all straightforward stuff such as slightly lowered suspension and so on.However there was one thing that has me stumped[not too difficult!!]and that is Black daylight opening ???Now I've asked a few Ford techies and a couple of Ford sales people about it and got the same answer,"Dunno,never heard of it"So I thought I'd ask the font of all knowledge that is OOF.What is it?What is it for?What does it do?Why is a black one better than any other colour?

[Doctor Gollum]

3.22 Daylight Opening DLO—Daylight Opening is a line on the exterior glazing surface that defines the minimum unobstructed opening through any glass aperture, including opaque coatings, reveal or garnish moldings adjoining the glass, according to a given direction or projection. Opaque coatings, reveal or garnish moldings adjoining the interior glazing surface are projected horizontally to the interior glazing surface, then normal and outward to the exterior glazing surface. Exterior components are projected horizontally to the exterior glazing surface (see Figure 3).

From...

https://law.resource.org/pub/us/cfr/ibr/005/sae.j1100.2001.html

Makes sod all sense to me But suspect that it's marketing wank for black trim

[STEMO]

Gotta be that black bottom half of the rear bumper. Maybe something to do with aerodynamics, or maybe just so you can see through to the go faster bits.