Portal tombs, sometimes called dolmens, are Neolithic megalithic structures in which large upright stones frame an entrance to a burial chamber, with one or more enormous roof stones laid across them. What gives this one an additional layer of interest is its name. The first edition Ordnance Survey map records it as Leac an Scáil, and the translation has been disputed for two centuries. Writing in 1802, Mary Tighe rendered it as something close to "the Great Altar Stone", which scholars have since regarded as incorrect. William Borlase, writing in 1897, interpreted "scal" as meaning a champion, while Canon William Carrigan, in his 1905 history of the diocese of Ossory, preferred "Rock of the Hero". The heroic reading has endured, and it suits the scale of the thing.

The tomb is orientated NE-SW, with two tall portal stones forming the threshold of the burial chamber and a massive high-pitched capstone resting on a secondary roofstone rather than directly on the portals themselves. The chamber itself is stone-lined, defined by side stones, a back stone to the south, and a sill stone to the north. Along the eastern side of the monument there are faint traces of a low retaining cairn, the kind of rubble mounding that would once have packed around the base of such a structure. More intriguing is what has disappeared entirely: William Borlase noted in 1897 that the tomb had formerly been surrounded by an embankment or rath, a roughly circular enclosure that would have set the monument apart from the surrounding landscape. No trace of that enclosure is visible today. A standing stone survives approximately a hundred metres to the south-west, hinting that this corner of Harristown was once a more densely marked ceremonial or funerary landscape than what remains above ground now suggests.