A togher is a causeways of timber and brushwood laid across soft, waterlogged ground to allow passage where the earth would otherwise swallow a traveller whole. This particular example is a slender thing: just one and a half metres wide and barely twelve centimetres deep, its timbers oriented roughly east-north-east to west-south-west, as though someone once needed urgently to cross from one dry patch of ground to another.

The construction follows a technique that was widespread in Irish wetlands for millennia. Lengths of roundwood, likely cut and trimmed locally, were laid lengthways along the route, with brushwood of ash and alder packed alongside or beneath to spread the load across the bog surface. Alder in particular was well suited to this work; it is one of the few timbers that hardens rather than rots when kept permanently wet, which is precisely why so many toghers have survived at all. The bog itself acts as a preserving medium, cutting off the oxygen that would otherwise allow decay. What remains in Derraghan Beg is a class 3 togher, a designation that reflects the relatively modest scale and construction method compared to the more elaborate multi-layered road systems found elsewhere in the Irish midlands.