15 ILCS 410/10b.5: Appointments.

For the appointment of a person standing among the 3 highest on the appropriate eligible list to fill a vacancy, or from the highest ranking group if the list is by rankings instead of numerical ratings, except as otherwise provided in paragraph (2) of Section 5c and Section 16 of this Act. If there are fewer than 3 persons in the highest ranking group, appointment may be made from the next lower group.