Entrance to adit with associated ramp that transferred slate blocks from the underground working of Diffwys quarry to the mill on Floor 0. This was in use in 1889 at the date of the 1st edition Ordnance Survey but was disused by c.1900 and the 2nd edition Ordnance Survey.

A simple rock cut adit entrance, from which the ramp down to Floor 0 is now covered in vegetation and rubble. A series of retaining walls and inclines surround this complex.

Louise Barker, RCAHMW, October 2015