Portal tombs, sometimes called dolmens, are among the most immediately recognisable of Ireland's prehistoric monuments: typically two tall upright stones forming an entrance portal, a lower backstone, and a large capstone tilted at an angle across the top, the whole arrangement once covering a burial chamber. What makes any surviving example worth attention is simply the improbability of its continued existence, thousands of years of weather, farming, and human interference notwithstanding.

The Ballyknock tomb was documented by Ruaidhrí de Valera and Seán Ó Nualláin in their 1964 volume covering County Mayo as part of the Survey of the Megalithic Tombs of Ireland, a systematic county-by-county catalogue of Ireland's prehistoric funerary monuments. De Valera and Ó Nualláin's work remains a foundational reference for understanding how these structures were distributed across the landscape and how individual examples compare in their dimensions and state of preservation. Mayo is particularly rich in megalithic remains, and the Ballyknock example represents one of the westernmost concentrations of portal tomb tradition in Ireland, a tradition associated broadly with the earlier Neolithic, roughly the fourth millennium BC.