Robin Hood and Little John 2
Image by Kammer

and those nine days are just about the length of the present day Christmas festival - alright then - twelve.

I'm working on the theory that stone monuments were 'roughed out' in drystone often, to test alignments and appearance. Sighting posts may have been made by this method and would leave virtually no archaeological 'signature'. Just because they're not needed doesn't mean that they weren't used. 'Measure twice, cut once'.

I know that the horizons were marked in the North Pennines by these curricks - but I don't know why these markers are there. When they're in place they are excellent almost-unconscious reference points.

By moving round in a landscape, and finding the best spot to see them all from, is an excellent way of tracing back to relic monuments. It takes weeks of fieldwork though. And it's only possible in a relatively unpopulated area, otherwise the stone would quickly have been reused, usually as wall.

david !

"roughed out in drystone often, to test alignments and appearance. Sighting posts may have been made by this method and would leave virtually no archaeological 'signature'"

You could also speculate whether some stone monuments were long preceded by wooden ones. Replacement in stone would obscure the signature - except, perhaps, in the case of your now-removed sighting stones. In those cases there is now no pointer as to where the original postholes should be sought.
OK, it's a speculation on a speculation but there are so many postholes being discovered "by chance" that there might be some really significantly aligned ones still to be found.