Player Core
Chapter 7: Spells
Walls
Source Player Core pg. 301
Spells that create walls, such as wall of plasma, list the depth, length, and height of the wall, also specifying how it can be positioned. Some walls can be shaped; you can manipulate the wall into a form other than a straight line, choosing its contiguous path square by square. The path of a shaped wall can't enter the same space more than once, but it can double back so one section is adjacent to another section of the wall.