This unusual arrangement is what marks the site out. Most court tombs, a type of megalithic monument built by Ireland's earliest farming communities roughly five to six thousand years ago, consist of a single roofed gallery of chambers preceded by an open semicircular forecourt. At Farnoge, the design appears to have been doubled, with two such galleries set in opposition along a north-east to south-west axis, the whole structure stretching approximately fifteen metres in length.

The monument was studied and described by Ruaidhrí de Valéra and Seán Ó Nualláin in 1962, and what they recorded was already in a heavily ruined state. The south-western gallery, five metres long, has lost its front portion entirely. What survives is a gable-shaped backstone, two sidestones, and two opposing jamb-stones set slightly inward, a feature typical of the internal divisions found in court tomb chambers. A single sidestone remains from the second chamber further along. A field bank, built at some later point, cuts across the monument here, likely displacing or burying further material. The north-eastern gallery, six metres long, is even more disturbed, though it follows a similar pattern: a backstone, one surviving sidestone, and two inset jambs. At the outermost end, one stone may represent an entrance jamb or portal. No trace of the forecourts that would have given the tomb its classification survives above ground, but the back-to-back gallery plan is itself characteristic of what is known as a dual court tomb, a rare variant within an already uncommon monument type.