A bond mutual fund is an investment company that manages its own portfolio of multiple bonds. Investors buy ownership in the company, and the company buys and sells bonds with the goals of the fund in mind. Since it contains multiple bonds, so you can’t lock in the payment rate like you can by purchasing a bond directly. However, the bond manager can invest in a large number of different funds, which might not be possible for an individual. The fund must also buy back your shares at any time. If you wish to sell a bond you invested in on your own, you’ll have to find a buyer for it.