34 CFR §681.17

1. (a)A HEAL loan must be made without security.
2. (b)With one exception, it must also be made without endorsement. If a borrower is a minor and cannot under State law create a legally binding obligation by his or her own signature, a lender may require an endorsement by another person on the borrower's HEAL note. For purposes of this paragraph, an “endorsement” means a signature of anyone other than the borrower who is to assume either primary or secondary liability on the note.