Bonds rated AAA by Standard and Poor's or Aaa by Moody's that are issued by sovereign governments, government agencies, and companies exist in insufficient supply in order to meet the needs in financial markets: needs being owning these bonds as investments, and for use as collateral for financial transactions $--$ both being very large markets. The total need for AAA$/$Aaa bonds can be met by alternative means $--$ using debt that is not AAA$/$Aaa rated. How does that process work $--$ i$.$e$.,$ how can you make AAA$/$Aaa rated debt by using bonds that possess lower credit ratings?