A field survey of Cooleeny townland identified 44 toghers, the term for a bog road or causeway built from timber and other organic material, laid across waterlogged ground to allow people and animals to cross terrain that would otherwise have been impassable. The sheer number of them in a single townland suggests this stretch of bog was not a barrier but a crossing point, threaded through repeatedly over generations.

The construction methods vary considerably across the 44 examples. Most combine brushwood, the smaller branchy material cut from trees and shrubs, with roundwood, the straight-cut poles and rods. Six toghers used roundwood alone, eight relied entirely on brushwood, and one unusual example incorporated gravel alongside the brushwood. Two of the toghers have been radiocarbon dated, both falling within the Iron Age: one to between 388 and 207 BC, the other to between 372 and 192 BC. These dates place their construction during a period when bog trackways were being laid across Ireland and Britain with some regularity, likely serving seasonal movements of people, livestock, and goods. Where wood species could be identified across seventeen of the toghers, the range is notably broad: alder, ash, birch, blackthorn, hazel, mountain ash, and willow all appear, pointing to opportunistic use of whatever timber the local environment provided rather than any single preferred material. That variety also tells something about the landscape around Derryville Bog in the Iron Age, one in which mixed woodland and scrub grew close enough to the wetland edge to be readily harvested.