Worst-case scenario: the UEd Goblin wipes the map and burns down your house.
Legacy:Texture Rotate
From Unreal Wiki, The Unreal Engine Documentation Site
This mode rotates a texture smoothly to any angle. The rotation is centred on one vertex of the selcted poly. I'm really not sure how UEd decides which one.
Anyway.
Hold down the CTRL key, then left or right mouse button. Move left to rotate the texture clockwise, or right for anti-clockwise.
That's it.
