These are toghers, the Irish term for trackways laid across waterlogged or impassable ground, constructed by weaving and stacking timber to create a firm surface over otherwise treacherous terrain. That so many should be concentrated within a single townland, Cooleeny, suggests this was no casual crossing point but a place that generations of people needed to move through, repeatedly and purposefully, over a very long period.

A field survey carried out by Gowen in 1999 documented the full extent of these trackways and the variety of methods used to build them. Most were made from a combination of brushwood, the smaller cut branches and stems, and roundwood, meaning timber in its natural rounded form rather than split or shaped. Six toghers used roundwood alone, eight relied entirely on brushwood, and one unusual example incorporated brushwood and gravel together. Seventeen of the toghers were examined closely enough to identify the wood species used, and the range is striking: alder, ash, birch, blackthorn, hazel, mountain ash, and willow all appear, suggesting builders were selecting from whatever timber was locally available rather than following a strict preference. Two toghers were radiocarbon dated, placing their construction firmly in the Iron Age. One returned a date range of 388 to 207 BC, the other of 372 to 192 BC, meaning people were laying these roads through Derryville Bog at roughly the same time that the La Tène culture was transforming metalwork and art across much of Europe.