The goal for the tablets is not for visibility, it was to install permanently installed points of reference at points about 900 yards apart and at all angles in the property line. The best permanent point is something that will not easily be moved or removed and will last for the long term. The tablets are typically drilled in and bonded to ledge even if that required digging to reach ledge. In areas where ledge is not accessible they do use tablets mounted on iron pipes. In some cases the pipes are tight in the ground but in other places they are loose or just installed in pile of rocks. The tablets are intended to be there long term to allow the property lines to be recreated. One of the "rules" of surveying is "monumentation", physical long term markings on the ground take precedence over plot plans, distances and angles so the monumentation is the highest priority to maintain but not necessarily make obvious to the general public. Especially with current technology, the boundary points can be located with differential GPS to a 1 to 3 centimeters so even if the tablets are buried a determined surveyor with the right gear is going to know where to dig to find the tablet. There are witness trees established nearby each point that give distances and bearings to each tablet. We also are supplied plastic boundary markers to attach to trees that are usually attached at obvious paths and woods road crossings as well as near tablets.
One of the other things about older surveys is the corners and acreage were very approximate and subject to interpretation. Having a licensed surveyor drive pins or set a tablet sometimes establishes a definite point for what was an indefinite boundary. The same applies with ax blazes and paint spots. If the abutter does not agree,its up to them to hire a surveyor to establish a line and if they dont agree the parties can go to court where the judge decides which surveyors opinion is best supported by the evidence. In the case of the AT relocation in the 1980s it was timber companies selling what to them was low value ridgeline land not that suitable for forestry so when the NPS spent the time and money to research, survey and mark a line I dont expect there was lot of complaints.
The line was marked when surveyed, with some exceptions, like vertical cliffs, with ax blazed trees painted with yellow markings The trees on the actual line are blazed aligned with the boundary while the trees to the left or right are blazed facing the line. There are couple of problems with painted ax blazed trees, some die, some heal the ax blazes, and paint on bark needs to be renewed. In some places the prior owners gave the lots a "haircut" before they sold the land so suitable mature trees were just not present to mark. These boundaries are rarely cut paths and boundary maintainers are warned not to turn them into paths although some of the pro boundary marking crews seem to have more latitude and cut quite a swath. Given that the vast majority of the AT in Maine is rural woodland the abutters are mostly wood lot owners and in theory responsible for assuring that they only cut on their own land. In areas with more population and higher value lands near ponds and rivers, the line is more aggressively maintained and monitored. The AT in Maine is roughly 281 miles out of 2200 miles for the total trail (12.7%) and is definitely the most rural with the least population base so getting volunteers to just cover the trail maintenance let alone the north and south boundaries is a major challenge. ATC does on occasion fund paid crews and there are volunteer college crews that do repainting but they are definitely in catch up mode. The federal government paid for the initial survey but the ATC and its delegated partner MATC for most of Maine (north of Grafton Notch) are responsible to maintain the corridor. The corridor monitors are supposed to walk the lines yearly and keep an eye out for trespass but given the ruggedness of my section its taken me several years just to locate the line in the woods. I also lost access to one of my access points for several years so half of my section required hiking up and over a mountain in the AM and the PM to even get to my boundaries which meant only 3 or 4 hours or actual fieldwork. I was just starting to get to the point where I could start repainting blazes and after 30 years the paint and blazes are very hard to find especially solo.
.
