What Is That Red Line

[[RDH]Diversion]

When I saved it, a red line appeared on my blueprints. It looks like it was drawn there or something, what is that and how can I get rid of it?

[Darth Draugmahl]

Sounds like the map editor has determined that your map has a leak. Follow the line whereever it interesects with the outermost and see of there is a whole that allows you to "see" into the void (The area outside your enclosed map area)