Zig-zag stones are plentiful about the roadsides and field edges, though more commonly of an erect aspect with bent 'head'. Often where you find a pair of stones they will be of dissimilar shapes (especially where the major faces are aligned). And often enough one will be of such a form as says their choice not simply functional for gateposts (more especially the flat-face aligned pairs, unless it be on occasion for an hypothesized precursor of the 'Orkney gate'). And the ones at Newbigging would seem to far exceed even 3.6m apart.