The system is made up of rectangular and sub-rectangular fields, each no more than around forty to fifty metres at their widest, aligned on a rough north-west to south-east axis. The enclosures are formed partly by earthen banks, roughly 1.7 metres wide and half a metre high, with large stones worked into their fabric, and partly by something more minimal: single lines of close-set stones and boulders, with some set transversely across the line of the wall, a technique that helps bind the structure laterally. The banks and walls mostly run straight, but meander where they meet natural rises or outcrops of rock, giving the whole system the slightly organic quality of something that grew with the land rather than being imposed upon it.

What makes the Rockfield system particularly interesting is the way it relates to an older monument nearby. At the south-eastern edge of the field system sits a rath, which is a roughly circular earthen enclosure of early medieval date, typically used as a farmstead or place of settlement. The field boundaries do not cut through this rath; they stop short of it, respecting its outline. That deference is significant. Cultivation ridges, the raised parallel strips of soil thrown up by repeated spade or plough work, are visible inside the fields themselves, but they also appear within the rath, suggesting the older enclosure had already been long abandoned and repurposed as agricultural ground by the time the field system was laid out around it. Taken together, the orientation of the ridges and this relationship with the rath point to the field system being post-1700 in date, likely part of the reorganisation of agricultural land that was widespread across rural Ireland in the eighteenth and nineteenth centuries. An enclosure lies at the north-western limits of the system, and a further earthwork sits approximately twenty-five metres to the south-south-west, hinting that this corner of Mayo was layered with activity across many centuries.