The feature is a rath, the Irish term for a ringfort, a type of enclosed farmstead that was the standard unit of rural settlement across Ireland from roughly the early medieval period through to around the twelfth century. Tens of thousands once dotted the island; this is one of the survivors, imperfect but still legible.

The raised interior of the Corglass rath measures approximately 41.2 metres in diameter, enclosed by a low earthen bank with the remains of a fosse, the shallow ditch that was dug to provide the material for the bank and to reinforce the boundary. The combination of bank and fosse was a marker of status and a practical deterrent, keeping livestock in and unwanted visitors out. Modern field boundaries now cut across the outer foot of the bank on the north-western to northern arc and again on the south-south-eastern to south-south-western side, meaning the agricultural reorganisation of later centuries has clipped and partially obscured the original circuit. A possible original entrance is thought to have been positioned at the south-south-east, a south-facing orientation that would be consistent with many comparable sites elsewhere in Ireland.