This is the cover of the westward continuation of the same E-W drain covered to the east by 5739. Based on the resemblance to diagonal drain covers 5871 and 5876 in Room 22 in the southwest corner of the lower terrace, both of which seem to be related to a later reorganization of the space, this SU was differentiated from 5739, with which it had originally been grouped during the 2014 excavation season. Unlike the slabs 5739, the slabs of 5907 are less regular in shape and size (one of them seems to be a repurposed threshold), and do not closely fit against wall/threshold 5740/5741. They sit well below the level of threshold 5740 to the south and floor 5726 to the north, and this would seem to have made for too awkward a transition to be original. With these considerations in mind, this seems to have been related to a repair to the drain and/or a repurposing and reorganization of this space, after the original surface had been disrupted or spoliated, and not to belong to the original phase of the building.