Unlike the familiar vertical waterwheel, a horizontal mill, sometimes called a Norse mill or click mill, drove its millstone directly from a wheel laid flat in the current below, the force of the water spinning the stone above it through a single upright shaft. It was a technology well suited to the smaller, faster streams of the Irish countryside.

What came to light that year were two key components: a section of wooden trough, measuring 1.5 metres long by 0.4 metres wide, which would have carried and directed the flow of water from the stream into the mill structure, and a millstone, the workhorse of any grain-processing operation. The trough in particular is the kind of find that does not survive often; organic materials tend to disappear over centuries, and its preservation points to conditions at the site, perhaps waterlogged ground near the stream, that slowed decay. The millstone, by contrast, is the more durable element, and millstones from horizontal mills have been found across Ireland, though the full assemblage of wooden and stone components together is less common. Adding further interest to this small area of north Mayo is the presence of a possible metal-working site recorded nearby, suggesting that this stream-side location may once have supported more than one kind of industry.