The mound is twelve metres across and only about sixty centimetres high, the kind of feature that could easily be mistaken for a natural rise, were it not for what it is made of: the cracked, fire-shattered rock that is the calling card of a fulacht fia.

A fulacht fia is a prehistoric cooking site, typically found near water and in low-lying or boggy ground. The method involved heating stones in a fire and then dropping them into a water-filled trough to bring it to the boil, a process repeated until the stones cracked and fragmented from the thermal stress. Over time, the discarded burnt material accumulated into a horseshoe-shaped or circular mound around the trough. Thousands of these sites survive across Ireland, dating mainly from the Bronze Age, though some may be later. The Shanaknock example fits the type closely: marshy ground, proximity to a stream, and a mound composed of burnt material. A possible opening about three metres wide faces north-west, which may indicate where the trough once sat. What gives this particular site a small additional footnote is that it was recorded as early as 1937, when a researcher named Broker noted it on the land of a Mrs Denis O'Connor, describing it then as round, roughly four yards across, and two and a half feet high. By that account, it had already been partially removed around 1930 to provide material for a fence, which likely explains why the mound stands a little lower today than Broker's original measurements would suggest.