The eastern end of a wedge tomb, a type of megalithic burial monument characteristic of later Neolithic and early Bronze Age Ireland, was absorbed into a field fence at some point, blurring the line between ancient funerary architecture and the workaday infrastructure of farmland. Wedge tombs are so called because their galleries typically taper in both height and width from front to back; this one is aligned roughly east-northeast to west-southwest, the orientation shared by most examples of the type, with the wider, taller end generally facing the setting sun.

What survives at Knockglass is the eastern portion of the gallery, with an estimated length of around 4.2 metres and a width of just 0.55 metres at its eastern end. Three opposing pairs of sidestones line the north and south walls, and a backstone sits outside the gallery walls at the east end. Along the north side, four outer-wall stones remain, with two further stones visible to the south. A displaced roofstone rests above the gallery rather than sitting properly in place, and traces of a low surrounding mound are still faintly legible, merging into the fence line to the west. Ruaidhrí de Valera and Seán Ó Nualláin recorded the monument in their 1982 survey of megalithic tombs across Cork, Kerry, Limerick, and Tipperary, and the structure sits on a gentle south-west-facing slope that looks out over the River Laney valley. The field fence that had incorporated the monument was removed after the site was inspected, leaving the stones somewhat more legible as a tomb than they had been for some time.