70 ILCS 2605/4.9
From the return or reports of examiners, or from the examinations which he or she has made, the Director shall prepare a register for each grade or class of positions in the classified service of the sanitary district of the persons who shall attain such minimum mark as may be fixed by the Director for any part of such examination, and whose general average standing upon examination for such grade or class is not less than the minimum fixed by the rules of the Director, and who are otherwise eligible; and such persons shall take rank upon the register as candidates in the order of their relative excellence as determined by examination, without reference to priority of time of examination. The Director may substitute categories designated as A, B, and C for numerical ratings and establish eligible registers accordingly. The notice of examination shall specify the category or categories upon which selection will be made.
70 ILCS 2605/4.9