Red Brush Hill, Wrentham

I climbed up hill mostly next to the phone line, then over and down. It seems like I kept seeing a feature consisting of an outline against a boulder. This is a pattern that was familiar already from Borderland State Forest - a bit to the north. So here are examples from Red Brush Hill.
Note the small circle to the left of the larger rock:

Another, different and newer:

(from above)

And another (ain't this pretty?)

(from above, clearly with modern intervention)

It is modern but consistent with older things here.