Walls with Hollows

The woods in northern Upton, just south of the Mass Pike, have frequent examples of short walls that start and stop within 60 feet or 300 feet. FFC and I were wondering about how, maybe, they were meant to be seen from a distance. We also were wondering about shadows formed by the walls. But, in any case, sharp eyed FFC noticed some hollows at the ends of one of these short stretches of wall:
Here is a closeup of the end of the wall to the right in the above picture (sorry about the blur):
This reminds one of the current hypotheses about hollows: they are either as a place to sit, a remnant of a collapsed space, or where someone dug a hole.

In the example above, FFC thought there were hollows at either end of the wall. I want to mention this as part of the context of the general discussion about hollows in rock piles.