It is made almost entirely of burnt and fire-cracked stone, the accumulated debris of prehistoric cooking. This is a fulacht fia, a type of ancient outdoor cooking site found in enormous numbers across Ireland, typically Bronze Age in date. The usual interpretation is that stones were heated in a fire and then dropped into a water-filled trough to bring it to a boil, with the discarded, shattered stones gradually building up into exactly this kind of mound. The one at Knockastuckane measures roughly 6.6 metres north to south and 5 metres east to west, rising to about 0.45 metres at its highest.

What makes the site quietly interesting is that it does not stand alone. It is one of a cluster of three fulachta fiadh in the same area, suggesting that this particular spot was returned to repeatedly, or that several such sites were in use at the same time. Clusters of this kind are not unheard of across Ireland, but they hint at a level of sustained activity in the landscape that a single mound would not. The other two sites in the group are recorded nearby, though all three survive as unexcavated earthworks, so the precise relationship between them remains open.