These pictures are examples of markers for the buried control cables for Minuteman and Peacekeeper missiles in the area covered by Warren Air Force Base. In the wide shot you can see another marker in the background. In this particular case the location was E-8 (to the left of the picture), near the tri-state border. They often have arrows to indicate the direction the cable runs but in these cases the arrows are missing (or have blown off!).

This is a picture of an arrowed post.