They serve as a manpower management tool when used in conjunction with the officer designator codes.
These codes are entered in the Manpower Authorizations (OPNAV Form 1000/2) to indicate the categories of officers required for the billets.
The final (fourth) digit denotes the officer's current type of commission.
URL officers are also eligible to command shore installations, facilities and activities directly supporting the Navy's warfare mission.
The eight staff corps (and one Flag Officer) designators are:[1] Officers of the line, or staff, as appropriate by their career field, of the Regular Navy and Navy Reserve appointed for the performance of duty in the broad occupational fields indicated by their former warrant designators or enlisted rating groups.
Officers of the line, or staff, as appropriate by their career field, of the Regular Navy and Navy Reserve appointed to chief warrant officer for the performance of duty in the technical fields indicated by former enlisted rating groups.