they've been around forever. the ability to isolate a portion of a map to work on it is pretty much a standard feature of any BSP editor. certainly it exists on all the versions of radiant i've ever used
That's what I expect, but I never saw it, nor encountered it in the tutorials that taught me how to use Hammer. :hmph: And so now, after hundreds of hours of mapping, and finally being on the last 2 hours until the map release, I find it. Yay!