This is a togher, an ancient Irish term for a trackway laid across wet or boggy ground, and the one recorded at Derrynagran is a particularly considered piece of construction. At 1.7 metres wide and surviving to a depth of 0.45 metres, it is modest in scale but intricate in its making.

The trackway runs on a northwest to southeast orientation and is built up from five superimposed layers, alternating between longitudinal and transverse roundwood, with thinner brushwood packed in between. The roundwood timbers average about ten centimetres in diameter, the brushwood around five. This kind of layering was a practical solution to a real engineering problem: soft, waterlogged ground that would swallow an ordinary path. By stacking timber in opposing directions, builders distributed weight and resisted the shifting of the surface underfoot. The species identified in the Derrynagran togher include ash, oak, and birch, all trees that would have been readily available in early Irish woodland. One birch rod was dressed along its entire length, meaning it was deliberately shaped or smoothed, a small but telling detail that suggests deliberate craft rather than rough improvisation. Toghers of this kind are found across the Irish midlands, where extensive boglands made overland movement difficult for much of the year, and they range in date across several thousand years of Irish prehistory and early history.