Barclays and HSBC are on different ends of the mortgage crisis but between them they lost $6 billion from their exposure to the U.S. housing crisis and related credit crunch. HSBC lost money because of U.S. mortgages going bad, and Barclays lost money because of collateralized debt obligations (CDO’s) based on U.S. mortgages. The process of putting together a mortgage pool begins when a home loan is originated by a bank or mortgage lender. That loan is typically sold to a Wall Street firm that pools it with thousands of others. Once a pool is packaged, it is sold to investors in different slices, based on risk. That is the CDO.