I'm a doctor, not a mechanic
From Unreal Wiki, The Unreal Engine Documentation Site
This is a type of brush solidity.
- Nonsolid brushes are additive
- They don't block players
- Used for things like zone portals and Making Liquids
- May intersect add and subtractive brushes
- Must not touch or intersect other nonsolids or semisolids
 Related Topics
- Nonsolids are Built with CSG
- There are general Topics on Mapping
- Brush Hacking can turn nonsolids into subtractives
Dorkorama Considering that UnrealEd is dead and only part of its remains were incorporated into LevelDesigner.com , this page, and any others like it if there are any, needs a bit of fleshing out.
Tarquin: maybe someone should contact LevelDesigner to ask them if they'd like to donate the stuff they're no longer using. Though I doubt they would.
Copperman: If I'm not mistaken, non-solids may abutt each other edge to edge without any problems.