How to lock in the +5% interest rate from Fed Bonds?

Buying a fund does not do that, look at look at FXNAX and FTBFX for instance, lots of volatility and negative returns. Does buying a individual bond and holding it to maturity ensure the rate? I am looking at this wrong? Is there a way to buy individual securities like that with Fidelity or Vanguard?

I am looking to park a fairly substantial amount for ~6 months. Should I just get a CD instead?