...one could walk right by them on the trail.
So this illustrates the problem with the cairns and GPS, maybe not signs. The trail along the top of the Trapps from Sixish North until the Arrow wall is quite far back from the cliff edge. It's maybe 500 feet back and in most places is fairly steep and there are many interspersed smaller sub cliff bands and or thick vegetation.
So this creates many problems with cairn idea. The main problem is that I don't think any climbers walk all the way up to the Trapps cliff top trail(between Sixish & Arrow). There are smaller trails that connect the tops of climbs with the nearest cliff top anchors and from visible use you can see where most people travel and it is the line of least resistance. I encourage everyone to go up there and see for yourself.
But, lets say I am wrong or that you could change climber behavior so that climbers in the area N of Sixish, S of Arrow would walk to the cliff top trail, locate a cairn, then walk down through the woods. This would lead to acceleration of the erosion that has already started to break into the soil for the Arch & Three Pines rappels. I will post pictures of this soon.
The second problem is that you can't really build cairns anywhere else because the hillside is so steep that you would be piling up rocks on a steep slope above a rap anchor.
On a side note the cliff top trail had been painted with blue rectangles very similar to the markings found on the Millbrook Ridge Trail, but they have been painted over with grey paint. Also, someone has already attempted to mark the bolted rappels by painting three equidistant black circles on rock near the descents.
So I see three different areas that have different issues:
Region 1 Belly Roll to Frog's Head, there is a spiders web of cliff top trails. Lots of tree anchors with tree bark suffering, exposed roots, lots of erosion, three instances of the formation of gullies.
Region 2 Frog's Head North to Arrow, Erosion is minimal with the exceptions of soil starting to be exposed at Arch and Three Pines. Shockley's/Strictly erosion is really bad and the Middle Earth rappel has killed two large pine trees and is heavily eroded. Most trails in this region are sub trails used by climbers to walk from the top of their climb to an adjacent rappel anchor.
Region 3 Arrow North to High E, there are basically no erosion problems. You could build cairns here and this would probably help some people in locating them.
Of course all of my observations are subjective, so if you want to see for yourself it's a short and pleasant hike that is worth doing now that the chiggers are done for the season and the leaves are down. Although I have done this cliff top hike many times before I had never done it with the idea of anchor management and cliff top preservation in mind... it certainly opened my eyes!