Course of ashlar wall between and partially covering thresholds 5582 and 5583. This wall is abutted by floor 5585. Only the lower course is left, which was exposed after taking part of 5302 off of it. It's made of two tufo blocks and was part of the walls surrounding the cocciopesto floor and forming the eastern limit of Room 18.
Room 18 with floor, thresholds, and eastern wall