Roll-down returns come from maximizing a bond's yield by exploiting the yield curve. The yield curve is a chart that illustrates the relationship between the yields of bonds and their maturities. The curve typically plots the yield on the vertical axis and the time to maturity on the horizontal axis. In a roll-down situation, if you bought a bond that is now on the steeper part of the yield curve and you hold while its maturity shortens but market yields stay relatively stable, the bond's price will likely increase as it "rolls down" the yield curve toward its par value.