How does the Chief Justice of India designate a person to be an ad hoc judge?
From the given context, it can be inferred that the Chief Justice of India designates a person to be an ad hoc judge by:

1. Receiving a reference from the National Judicial Appointments Commission (NJAC) regarding the need for an ad hoc Judge due to unavailability of quorum among the judges of the Supreme Court.
2. Consulting with the Chief Justice of the High Court concerned.
3. Designating a qualified Judge of a High Court, after obtaining prior consent from the President.