That classification alone sets it apart from the thousands of ordinary ditches, walls, and hedgerows that divide the Irish countryside. A field boundary earns that status when its age, construction, or alignment suggests it belongs not to recent agricultural tidying but to an earlier, often much earlier, ordering of the land.

Field boundaries of this kind can range from Bronze Age land divisions, some of the oldest organised farming landscapes in Europe, to medieval or early post-medieval enclosures that reflect the rhythms of rundale farming, a communal system of strip cultivation once widespread across Connacht. In Mayo particularly, where blanket bog has preserved ancient field systems beneath its surface, even an unassuming line of stones can turn out to predate written history entirely. Carrowmore, as a place name, derives from the Irish An Cheathrú Mhór, meaning the big quarter-land, a unit of landholding that itself speaks to centuries of agrarian organisation in the west of Ireland.