“Tack indicates location of poster.”
We found this survey marker by the Tar Kiln Trail in Piney Creek Wilderness. It’s quite hard to see, but I was able to make out that the tack in the center marks the place where this post is on a grid.
Forest Service Location Poster survey marker found on the Tar Kiln trail of Piney Creek Wilderness
I believe this is a reference marker, or “bearing tree”. It means that it points to where the actual survey marker is (or would be if practical). This sign indicates that the marker is 8 chains* away, bearing west. As that direction was a very steep slope, I suspect this reference is all there is to indicate the marker designating the land corner. The 36 squares you see on this sign are the 36 square miles in a township.
Location:
Latitude: 36° 40.727’N
Longitude: 93° 35.686’W
*A chain is 66 feet. There are 80 chains in a mile. A parcel of land 1 mile square, known as a section, is 640 acres. A furlong is 10 chains. The side of a section is 8 furlongs long. Divide a section into furlong lengths, you get 80 acre parcels. So this explains why land is often sold in 40 or 80 or 160 acre sections.