The cut was original thought to be for the robbing of slabs of floor in room 19 (SU 5726) but excavation also reveals that the cut is associated with a brick arch feature (5757) opening on to room 16. The SU cuts through the slabs of 5726 and into the bedrock below and continues as a channel in the bedrock within room 16. This channel is directly aligned with the arch opening. The cut therefore seems to be part of either a water feature or some sort of fire feature (for cooking, industrial production, or heating).
Brick arch between 5664 and 5665 (5757), Broken-tufo slab and small rock below 5757 (5758), Rectangular cut in bedrock into slab floor 5726 (5759), and nearby walls 5664 and 5665