Here is a completed propped boulder.
Here is another propped boulder shown previously.
Near some of these boulders is this large rock with a strange "chair" shape. When I swept away the leaves, I found the "seat" is flat. This was probably not used in food production, but may have been used in making and edging tools. There might be tools and rock chips scattered around it.
I think this site shows the historical progression of Indian quarrying. First the Indians built these propped and oddly shaped boulders for their own reasons. After the white man came, they used their quarrying skills to break up boulders into squarish stones and build walls. Of course, it is impossible to be know exactly how the site was altered over time.
In less than two weeks, somebody added a tongue to the site guardian!