The main aim of securitization that was initiated in the late sixties was to resolve problems of mismatch and protect the US mortgage financing system from macroeconomic instability without forgoing, and credit rationing the presumed US friendly standard fixed-rate level payment mortgage which carried a fixed coupon interest rate, constant annuity payments, fixed maturity usually of 30 years and with an option for the borrower to repay fully or partly with the exercise price at par and without any termination option for the lender.

As the intermediary finally can sell only the cash flows contained in his asset portfolio, the mortgage design needs a relatively intricate long-term refinancing instrument which is a very long-term, fixed rate and callable refinancing vehicle. This could be attained by a combination of different varieties of instruments. Securitization of the entire package was seen as an elegant alternative. As a substitute of a complex on-balance sheet refinancing tool, the investor is offered exactly the cash flows that mortgage borrowers choose to make.