The term refers to a mound of fire-cracked stone and charcoal that accumulated beside a water source, the by-product of repeatedly heating stones in a fire and dropping them into a water-filled trough to bring it to the boil. Thousands of these sites survive across the country, yet most remain low, unremarkable humps in the landscape, their significance invisible to anyone who does not know what to look for.

At Ballyviniter, the site is visible in section along both sides of a channel that was cut relatively recently to redirect the stream running through the area. That engineering work, while not archaeological in intent, inadvertently exposed a cross-section of the monument, revealing burnt material to a depth of around one metre over a north-to-south span of twelve metres. The material dug out during the channel cutting, a mixture of burnt stone and boulder clay, was piled up on either side of the new channel, which means the full east-to-west extent of the site is now obscured beneath those spoil heaps. It is a small irony that the disturbance which revealed the site's depth also buried part of its footprint.