It is a fulacht fia, a type of site found in extraordinary numbers across Ireland, typically interpreted as a Bronze Age cooking place. The standard explanation involves heating stones in a fire, dropping them into a water-filled trough to bring it to the boil, and then using that hot water to cook meat. The stones crack and blacken in the process and are discarded in a characteristic horseshoe or oval spread, which is exactly what survives here.

What makes Knockagolig more than a single curiosity is the density of these features in this one area. A second fulacht fia lies just eleven metres to the west, and the two together form part of a cluster of four such sites in the immediate vicinity. This kind of grouping is not unheard of with fulachta fiadh, but it does raise questions about how intensively this particular spot was used, and over what period. A researcher named Bowman recorded a group of four fulachta fiadh in this general area as far back as 1934, suggesting the sites were visible and noted long before any formal archaeological inventory was compiled. Whether the four sites recorded by Bowman correspond to this same cluster has not been definitively established, though the possibility has been noted by O'Shaughnessy in 1997.