They appear as low, horseshoe-shaped mounds, typically dark with charred and fire-cracked stone, usually found close to a water source. The one recorded at Knockrower in County Kerry is a quiet example of a type that was once a routine feature of the Bronze Age world, roughly dated to between 1500 and 500 BC, though some sites push earlier or later than that range.

The accepted explanation for fulachta fia, arrived at largely through experimental archaeology in the twentieth century, is that they functioned as outdoor cooking sites. The method was straightforward: a trough, sometimes timber-lined, sometimes cut into the earth, was filled with water and heated by dropping fire-warmed stones into it until the water boiled. The discarded, shattered stones built up over time into the distinctive mound that survives today. Other theories have been proposed over the years, including use for brewing, bathing, or hide-working, and it is likely that not every such site served the same purpose. What they share is the evidence of repeated, organised burning and the careful management of heat. The Knockrower example sits within a county that has an unusually dense concentration of these monuments, Kerry's boggy, well-watered terrain having preserved organic and archaeological material that drier ground would long since have lost.