The lower of the two is a togher, the Irish term for a raised timber trackway built across soft or marshy ground, and it is a remarkably precise piece of early engineering once you start reading its dimensions. It runs east to west, measures 2.4 metres wide and about 25 centimetres deep, and is made largely from birch brushwood, thin branches averaging around 15 millimetres in diameter, laid longitudinally in an irregular layer. Occasional rounds of ash, some nearly 70 millimetres across, were incorporated alongside the brushwood, and marks of woodworking on the timber suggest the material was at least partly shaped before being laid down.

What makes this particular togher especially interesting is its position. It was not simply buried by accumulating peat over centuries; it was buried by another togher built directly above it. The upper trackway, a separate structure, was laid on top of this one, meaning that whatever gap existed between the two construction events, someone later chose almost exactly the same route across the same difficult ground. Toghers of this kind are known from bogs across Ireland, ranging from simple bundles of brushwood to elaborate arrangements of planks and pegs, and they can date from the Bronze Age through to the early medieval period. The layering here suggests the crossing point at Derrynagran held some persistent practical importance, worth maintaining or rebuilding across a considerable span of time.