Closing Sectors

[Jellybones]

This is a problem I have that I really need to know how to fix.
Closing Sectors.

I know how to make sectors, but some of them I make are completely closed and normal, and others are unclosed. How does that happen, and how can I fix it?

 

[Scarbo the Black Sheep]

Understand sidedef references. Take a linedef and change what sector it references.

 

[Jellybones]

Alright, thanks. It helped a lot.