Map > Load Pointfile Follow the red line to the hole, seal it up, unload the pointfile and reload it. When it asks you to browse for one, you've sealed all of your leaks. If the red line is coming from nothing check the origin (little white circle, make sure helpers are on) of the entity that's leaking, which should be at the start of the red line. You'll only be able to see the origin with the entity selected.