It is a togher, an ancient timber trackway laid across waterlogged ground to allow people to cross terrain that would otherwise have swallowed them whole. This particular example, recorded at Derrylough, is about as minimal as such structures get: just 56 centimetres wide and 10 centimetres deep, running east to west, and built from a sparse arrangement of longitudinal roundwood timbers, each no more than about 9 centimetres in diameter. It is, in essence, a footpath made of thin poles laid lengthways across a bog.

Toghers are classified by their construction method, and this one falls into class 3, a type defined by its use of longitudinal rather than transverse timbers. The slender roundwood used here suggests modest materials, probably cut from young trees or branches, and the sparse layout implies either economy of effort or the practical judgement that a light crossing was all the ground required. Such trackways were typically embedded in peat, which preserves organic material with remarkable fidelity, holding wood, leather, and even fabric in conditions that would destroy them entirely on dry land. The bog at Derrylough has done exactly that, keeping this fragile structure intact long after the communities who built and used it have left no other trace.