what are sectors with just a middle texture called

[unpleasantmarine]

https://streamable.com/v2z5k

 

so when i delete a sector in SLADE it removes the sector but the linedefs surrounding it now have only one texture and go up to the ceiling

 

is there a name for these types of sectors? and how do i make one manually

[Simomarchi]

In reality there is no sector behind the lines. You have deleted it so it is a void place in your map, just like the one outside the walls. If you enter this place with a noclip code you will experiment halls of mirrors everywhere.

 

What happens when you delete a sector is that (at least in the modern editing softwares) the lindefs that one time were shared between the deleted sector and the other one are now "property" only of one of them (the one that you haven't deleted). This means that they are interpreted as "one-side linedefs", or solid walls. They are shown in red on the automap (the default one at least) and blocks everything (movement, bullets and sound). Also they gain infinite height and therefore they need only a middle texture.

 

You have just said what is needed in order to make such a thing. You create a sector of the shape that you want and then you delete it, making a "pillar" inside of another sector. Then you texture the pillar and that's all. You can make decorations, columns and even walls between previous connected rooms with this simple method.

There is no specific function to create a "void sector". Just create one and delete it.

[Empyre]

It looks like you want to make a "pillar", but if you don't want that to happen, you can Join or Merge the sectors instead of deleting.  Experiment, and use CTRL-Z to undo it if the results are not what you want.