Sector not closed?

In Srb2DB when i open "Find Map Errors" i find so many unclosed sectors.
How do i close them?

Sometimes SRB2doombuilder has a hard time defining sector walls, and glitches tend to happen, I usually check sector mode to make sure my sectors are functioning properly before I continue, I'll point that out to you right now. And in my experience, it happens a lot when you paste multiple sectors at once, or split sectors in odd formations. One thing you can try is go around the map and complete the sectors yourself, but I can't guarantee how it will work. I know I'm not much of a help, I haven't used SRB2Doombuilder a lot, but I'm trying.

Finnaly a reply on this topic. Thanks for ur help also i figured how it works :

Choose 2 sectors and press J to make them a single Sector