Before I continue, I hate to sound rude, but I want straightforward answers and not ambiguous posts until the thread is closed and I gain absolutely nothing.
I am making a simple, geometric open-air level. When compiliing, it says it is leaked–so I try to caulk the whole level, or “sky” the whole level to no avail. What am I doing wrong? The surface tutorials are good, but the sky section is totally vague. Am I supposed to make a giant brush that covers the whole terrain? And even supposing it DOES compile, how can I stop it from doing that overlapping glitch that shows like a thousand overlaps of whatever you’re looking at?
I desperately need help, and I can not find any tutorial or thread that has useful, straightforward information. I constatnly come across closed threads or bad answers. 
In the case of a terrain map, it might be the right thing to do to create a big box, and apply a sky shader to it but in all other cases it’s a sure way to screw up your map further.