The mound is horseshoe-shaped, roughly twelve metres from north to south and nearly sixteen metres east to west, rising to about ninety centimetres at its highest point. Its opening, three metres wide, faces west. What makes this particular example a little unusual is an extra projection on the eastern side, extending four to five metres outward and forming what amounts to a third arm at the rear of the mound, giving it an asymmetry that sets it apart from the more regular horseshoe form.

A fulacht fia is a Bronze Age cooking site, typically found near water or in boggy ground. The usual method involved heating stones in a fire and then dropping them into a trough of water to bring it to a boil, which would crack and blacken the stones over time. The discarded material, those shattered, heat-reddened fragments, accumulated around the trough and built up into exactly the kind of low, curved mound visible at Knockskehy. Ireland has thousands of these sites, making them among the most common prehistoric monuments in the country, though the precise range of activities they supported, cooking, brewing, textile processing, or bathing, is still debated among archaeologists. The marshy, sloping ground here would have provided a reliable water source, which was essential to the whole process.