When part of 5302 was removed, this threshold was revealed leading to room 18 from the central courtyard. It is aligned E-W with the threshold of Room 3 across the courtyard (5344) and connects the open space in the E side of F (tufo slab floor 5321 and 5410) to room 18. It aligns on a N-S axis with 5583 and is slightly longer than it.
Room 18 with floor, thresholds, and eastern wall