The site is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, particularly in low-lying or waterside locations. The basic principle was simple: stones were heated in a fire and then dropped into a water-filled trough, bringing the water rapidly to a boil. The cracked and heat-shattered stones were discarded into a mound nearby, and it is these spreads of blackened, fire-fractured material that survive in the landscape long after everything else has gone.

At Lackendarragh, the burnt spread measures roughly two metres east to west and six metres north to south, and a layer of burnt material approximately thirteen centimetres deep is visible in cross-section where the riverbank has been cut by the stream. That detail, the material showing in the eroding bank of the Duvglasha, is quietly telling. It suggests the site sits close enough to the water's edge that the river itself is gradually exposing what centuries of soil and vegetation had buried. The association with running water is entirely typical; fulachtaí fia (the plural form) are almost invariably found near rivers, streams, or boggy ground, where water was reliably available and the soft ground made digging a trough relatively straightforward.