A fulacht fia is essentially an ancient cooking site, typically consisting of a horseshoe-shaped mound of fire-cracked stones surrounding a trough that would have been filled with water and heated using stones taken from a fire. Thousands of them survive across the island, mostly dating from the Bronze Age, and they are almost always found close to water.

The Rockspring example follows that pattern closely. Marshy ground lies roughly twenty metres to the south-east, providing the kind of reliable water source these sites required. By 1937, when Ordnance Survey mappers recorded it, the feature still read as a distinct mound on the six-inch map sheet. Sometime after that it was levelled, most likely through agricultural activity, but the evidence did not disappear entirely. A cross-section exposed in the field fence and drain on the eastern side of the field shows burnt material running approximately seven metres north to south and surviving to a depth of around 0.4 metres. Burnt stones are also scattered across the surrounding area, the characteristically fire-fractured debris that accumulates when stones are repeatedly heated and plunged into water over generations of use.

The site sits in ordinary farmland, its archaeology now folded into the texture of a working field boundary rather than rising above it. That kind of low-visibility survival is actually typical of many fulachta fiadh: levelled by ploughing or drainage, they persist as discolourations in soil sections, as anomalies in cropmarks, or as the faint crackling underfoot of heat-shattered stone.