Innate Attack Wall Thickness?

[evileeyore]

Originally Posted by Kelly Pedersen

No, sorry to be unclear. My feeling is that, by default, a Wall must be placed on a solid surface.

I"d say it has to be anchored. You could put a wall a few floors up between two buildings as long as both sides were connected to the buildings, or even as a obstruction off of one building/cliff/tall tree/airplane/etc.