Identifies additional specific information related to the service address (e.g., building, floor, room).
NOTE 1: Recommended abbreviations are contained in the United States Postal Service Publication 28, Postal Addressing Standards Secondary Unit Designators section.
USAGE: This field is conditional.
NOTE 1: Optional when the SASN field is populated, otherwise prohibited.
DATA CHARACTERISTICS: 4 alpha characters
EXAMPLE: W I N G
NOTE 1: Where WING is the second location designator for the following address example: 25W 450 ½ SW Camino Ramon Lane NW, Floor 12, Wing 2, Suite 23A.