Thanks to Nick Aitken for suggesting this page....

This photo featured in Stonechat.... as a competition....
What you need to know is that the spirit level is 1.2m long  (it isn't placed vertically...).  the wall is 40cm wide immediately below the coping.
HINT....

The winning entry and an analysis of the suggested faults can be found here... put pdf on box
are there more eg sloping stones - fencepost is more or less vertical so can guess right angle and thus level from that.
Can I have a hover over list of faults on the page?

Maybe have some find the joints photos, look at tregarth 343- need some diagonals, zipped.....


Adcock, Sean       


DRY STONE WALLING ASSOCIATION
CYMDEITHAS WALIAU CERRIG SYCHION

Canghennau Gogledd a De Cymru
North and South Wales Branches