HaloMods "Classic" Read-only Archive

Hello, I'm fairly new to making levels (been HMT and HHT'ing it for a while) and I've run into a problem. Every time I make a level (in GMAX, using Kirk's 9 step video tutorial) and compile with tool I get the error that some edges are open, breaking the sealed level rule. I've tried to find the edges (individually is a pain, if anyone knows how to search by edge numbers, pray tell), but when I find them, I do not see an opening. I tried to make the level inside of a box, so the level is technically sealed, but that didn't work. So here, after my long description is my question: How do I seal these "open" edges?

Thanks,
Hadokendude