It is roughly 3.2 metres wide and less than 20 centimetres deep, oriented east to west, and built from materials that would have been entirely ordinary to the people who laid them down: a single layer of birch brushwood along the centre, flanked on both sides by roundwood lengths of oak and birch. That combination, brushwood packed and edged with stouter timber, is the hallmark of a togher, the Irish term for a bog road or trackway. Toghers were essentially low causeways engineered to carry people, animals, or goods across ground that would otherwise have been impassable.

What makes the Derrynagran togher quietly compelling is the evidence of deliberate woodworking found on its timbers. Toolmarks were recorded on the material, which means the wood was not simply gathered and thrown down but shaped before use. That small detail connects the structure to skilled hands, to someone who selected timber, worked it with a blade or axe, and fitted it into a surface meant to bear weight and repeated use across wet terrain. The birch brushwood at the core averaged around 14 millimetres in diameter, fine and flexible, while the flanking roundwood ranged from 60 to 160 millimetres, giving the edges a firmer frame. It is a practical, considered piece of engineering, modest in its ambitions and exact in its construction.