S.C. Code § 30-7-40
The recordation of such an assignment or transfer as is mentioned in Section 30-7-30 shall, to be effective under such section, be upon the record of the recorded mortgage or other written instrument, except that it may be recorded elsewhere in the record for the recording of mortgages should there be no place upon the record of the recorded mortgage or other written instrument sufficient for the recordation of such assignment, in which event there shall be entered on the margin of the recorded mortgage or other written instrument whose assignment has been thus recorded elsewhere an appropriate reference to such recordation, giving the name of the assignee, the date of the assignment and the record and page where recorded.
S.C. Code § 30-7-40