All appointments of employees to which this subpart applies, other than temporary appointments, shall be probationary for 12 months from the date of appointment. A probationary employee may be discharged by the sheriff at his or her pleasure at any time before the expiration of 12 months from his or her appointment. After the employee has served for 12 months in the position to which he or she was originally appointed or employed under either the county or Sheriff's Personnel Merit System, the employee shall become a merit employee.