FFC sees a structure in the stone wall

My friend from Carlisle (FFC) often points out things I would miss. Here is a stretch of stone wall with a curious flat rock propped vertically in the middle - and placed equally distant from two flanking white feldspar rocks.

 

 

FFC also points out the other flat rocks placed in the wall on either side of the center, forming a sort of "fan" [visible best in the first picture].
To express the thought a bit more completely: it sometimes seems the shapes of rocks have meaning, or that the shape is representational. An intentional shape seems most likely when the rock is placed in a prominent way - for example on top of another rock; in the middle of a symmetric structure; or highlighted by white rocks.