The site carries the straightforward classification of enclosure, a broad term that in Irish archaeology can cover everything from the circular earthen banks of an early medieval farmstead to the remains of a ringfort or a field boundary of much earlier origin. What it looks like on the ground, how large it is, and who built it remain details not yet in circulation.

Gleann Chaisil itself, whose name suggests a connection to a cashel, which is a stone-walled enclosure typically associated with early Christian-period settlement in Ireland, sits in a county with an extraordinary density of prehistoric and early medieval remains. Mayo's landscape, shaped by blanket bog and glacial drift, has a tendency to preserve earthworks that elsewhere were long since ploughed away or built over. An enclosure in this kind of terrain could represent any number of periods and purposes, from a defended homestead to a ceremonial or agricultural boundary, and the name of the valley alone hints that the area may have had significance to early inhabitants. Beyond that, the record is, for now, largely silent.