Crossed Pair rock piles

One time in Groton I climbed a hill behind someone's house and found three rock piles, each consisting of two elongated rocks on top of a boulder.One of the three had the upper rocks crossed and I concluded that the others might well have been that way also until they got damaged. Then I saw other examples of crossed pairs in other places.This last one suggests a reason for such things - crossed pairs are the simplest way to mark a point on the horizon.