So uh, yeah. I got the newest SCMD 2 quite a while ago and haven't found any use for the buttons that make the locations red...yet.
As far as I know they're just red and rectangular, so if somebody would be so gracious as to tell me a few practical uses for these things I would appreciate it.

http://www.staredit.net/?p=oldwiki&s=112

Units are only considered to be inside an inverted location, if the unit touch all 4 edges of the location at the same time.

You can make a movement detection and detect that a unit moved by at least 1 pixel.
It finds usage in some activation systems like activating a triggered spell in a RPG.
The detection is faster than a 1x1 pixel location because in a regular location, the unit is considered to be inside the location, if it touches the plane of that location. With the inverted location it only has to move by 1 pixel to invalidate the bring and make it therefore detectable in triggers with the cost of only 1 location.

Oh, very interesting. Now I know why the maps I made to test inverted locations never detected units... Thanks guys.

Yeah, it would be nice if inverted locations worked the way they seem to imply: eg a bring trigger would execute when you had units anywhere except 'inside' the location, acting as a 'hole'. Unfortunately they do not.