With $100,000 to invest, an investor could put approximately $20,000 in each of five bonds, with the first bond maturing two years from now, the second maturing three years from now, and so forth. Thus, if interest rates rise, the investor will have some principal returned periodically, which can be reinvested in new bonds with a higher yield. If interest rates decline, some of the previous higher yields are locked up until those bonds mature.