Unusually, however, central banks in jurisdictions with fiat currencies may "create" new money to back its own liabilities, to theoretically unlimited amounts. In many countries, the central bank may use another country's currency either directly (in a currency union), or indirectly, by using a currency board. In the latter case, local currency is directly backed by the central bank's holdings of a foreign currency in a fixed-ratio; this mechanism is used, notably, in Hong Kong and Estonia. In countries with fiat money, monetary policy may be used as a shorthand form for the interest rate targets and other active measures undertaken by the monetary authority.