Whenever a position in the classified service is to be filled, the sheriff shall notify the sheriff’s office merit commission of that fact, and the commission shall certify the names and addresses of the three candidates standing highest on the eligibility list for the class or grade for the position to be filled, and the sheriff shall forthwith appoint to such position one of the three persons so certified. Such appointment shall be for a probationary period to be fixed by the rules, but not to exceed one year. On or before the expiration of the probationary period, the sheriff may, by presenting specific reasons for such action in writing, discharge a probationary appointee, or, with the approval of the commission, transfer him or her to another department within the sheriff’s office. If not discharged prior to the expiration of the period of probation and if no complaint has been made about the service rendered, the appointment shall be deemed permanent. To prevent the stoppage of business or to meet extraordinary conditions or emergencies, the sheriff may, with the approval of the commission, make a temporary appointment to remain in force for not to exceed sixty days and only until regular appointment can be made under sections 23-1721 to 23-1736.