Locally it was called 'Toorybrennel', but it also acquired the more prosaic title of 'the schoolhouse', a nickname that hints at later use, or perhaps just at the way islanders made practical sense of ancient spaces. It is a clochan, the type of drystone beehive cell built by early Irish monks, in which courses of flat stones are laid so that each ring slightly overhangs the one below, closing inward until a roof forms without mortar or timber. This particular example sits tucked within 'The Cashel', the walled ecclesiastical enclosure that forms the ceremonial and spiritual core of the island, pressed up against the south wall of Templenatinny church.

The interior repays attention for what it contains rather than its size. The doorway, facing north, is framed by massive single-stone jambs. Once inside, a wall bench runs along the west side, and directly opposite the entrance a narrow, deep window admits a thin column of light. Two aumbries, small recessed cupboards set at ground level into the south and east walls, would once have stored objects of some importance, whether liturgical or practical. Outside, the wall base is noticeably thicker, stepping inward at shoulder height to form a scarcement, a projecting ledge that runs around the full circuit of the structure. The clochan is conjoined to a smaller corbelled cell on its south side, and access to the whole complex comes via a narrow alley cut through the terrace revetment from the adjacent cemetery. The survey carried out by J. O'Sullivan and T. Ó Carragáin between 1997 and 2000, and published in 2008, recorded the structure in considerable detail, though it noted that the clochan had already been substantially rebuilt during earlier restoration works, meaning what stands today is partly a reconstruction of what once stood here.