They appear as low, horseshoe-shaped mounds, typically beside a stream or in damp ground, and for a long time their purpose was debated at length. The leading interpretation holds that they were Bronze Age cooking sites, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. The crescent shape of the mound is formed from the discarded, heat-shattered stone, accumulating over what may have been repeated use across generations.

The example recorded near Kilbeacanty, in south County Galway, sits within a landscape that has been inhabited since deep prehistory. Kilbeacanty lies in an area of east Galway characterised by gentle drumlin country and the kind of low, waterlogged ground that would have made a fulacht fia's need for a reliable water source easy to satisfy. Bronze Age communities in Ireland, roughly spanning from around 2000 to 500 BC, left these monuments in remarkable density, and their presence in a parish like Kilbeacanty is a quiet reminder that the land has been managed, worked, and gathered around for a very long time before any written record begins.