What's up with shapeable Wall spells?

Question

Wall of Brine says it creates a wall 10 ft/level long, 5 ft/level high, and 5 ft thick. It also says this wall is shapeable, using the '(S)' denotation. Shapeable, in this case, means:

If an area or effect entry ends with “(S),” you can shape the spell. A shaped effect or area can have no dimension smaller than 10 feet. Many effects or areas are given as cubes to make it easy to model irregular shapes. Three-dimensional volumes are most often needed to define aerial or underwat1er effects and areas.

(emphasis added)

Wall of Stone is also shapeable, and states:

A wall of stone is 1 inch thick per four caster levels

Which, unless you're CL 480, also doesn't meet that 10' minimum.

Wall of Thorns is a little less bad, labelled '(S)', but also saying:

You can make the wall as thin as 5 feet thick, which allows you to shape the wall as a number of 10-by-10-by-5-foot blocks equal to twice your caster level. This has no effect on the damage dealt by the thorns, but any creature attempting to break through takes that much less time to force its way through the barrier.

Which seems like a pretty clear 'specific-exception-to-a-general-rule' thing.

Wall of Lava is also shapeable, and is as thin as a wall of stone.

I'm a little bit confused about these spells. Which of them are actual exceptions to that 'you can't make it thinner than 10' ' rule? If any of them aren't, what are you supposed to do about that '(S)' in the description?

Answer 1

All of them

Intuitively, if a spell can be cast when it's impossible to meet a restriction such as the 10' minimum for each dimension, the intention for the spell is something different. For these walls it seems the intention was that they are treated as flat area, even though they must have a thickness. Effectively most walls are two-dimensional, and both of those dimensions must be at least 10'.

I came to this conclusion by looking at the 'effect' lines that were marked with (S), for example Wall of Stone:

Effect stone wall whose area is up to one 5-ft. square/level (S)

The effect is described as a square, not a cube, which by definition only has two dimensions. The thickness is in the description for realism, breakability, etc. The other spells have similar effects, although worded slightly differently. Notably, Wall of Thorns does have a three-dimensional effect, and therefore would be subject to the minimum if not for the specified exemption.

The text of the shapeable attribute is easily read as though it treats every effect as three-dimensional, but it says

Many effects or areas are given as cubes to make it easy to model irregular shapes. Three-dimensional volumes are most often needed to define aerial or underwater effects and areas.

(emphasis added)

Many, but not all, effects or areas are given as cubes. Some are given as other shapes, which may be two-dimensional. Such shapes must be exempt from the 10' minimum in their non-existent dimension.