A wedge tomb is a type of megalithic burial monument, typically a roofed gallery that narrows towards one end, built by farming communities in the centuries around 2500 to 2000 BC. At Kilnagarns, only the northern side of a single chamber survives, running roughly five metres on a northeast to southwest axis, with two façade-stones still standing at the western end, the taller reaching just over a metre in height. It is a stripped-down remnant, but that very incompleteness is part of what makes it interesting.

When archaeologist J. X. W. P. Corcoran excavated the site in 1964, he found traces of a cairn, the rubble mound that would originally have covered the stone structure, along with a single sherd of pottery tentatively identified as Beaker ware. Beaker pottery takes its name from its distinctive cup-like form and is associated across Atlantic Europe with a period of considerable cultural change in the late Neolithic and early Bronze Age. The excavation also turned up flint and chert fragments, though these were too indeterminate to point to any specific activity or period. What makes the Kilnagarns site especially worth noting is its immediate surroundings: a court tomb, a different and generally earlier form of megalithic monument, lies roughly twenty metres to the northeast, and a possible standing stone sits about fifty metres to the east. The clustering of monument types in such a small area suggests this hillside carried real significance for the people who shaped it, even if the precise nature of that significance is now beyond recovery.