Gah - a solution with more questions. – EntropicLqd
From Unreal Wiki, The Unreal Engine Documentation Site
Creates a sheet for the red builder brush
- Height - the height of the sheet
- Width - the width of the sheet
- Axis - The axis of the sheet, this can be horizontal (Z axis), XAxis or YAxis
- Groupname - doesn't work with it
The Sheet can be used for zone, portals, windows, whatever. Note that you can always go through the sheets, so they're bad walls.