Betting against a bond or bonds, often referred to as “shorting a bond,” involves taking a position that profits if the bond’s price falls. This is less common than betting on a bond’s price to rise, but it can be done in several ways:

1. **Short Selling**: This is the most direct method. You borrow bonds from a broker and sell them at the current market price, with the agreement that you will buy them back (at a lower price, you hope) at a later date to return them to the lender. If the bond price falls, you buy them back at a lower price, return them, and keep the difference as profit. However, if the bond price rises, you will incur a loss.

2. **Bond Futures**: You can sell bond futures contracts, which are agreements to sell a bond at a specified price at a future date. If the market price of the bond falls, the futures contract becomes more valuable, and you can profit from the difference.

3. **Options**: You can buy put options on bonds, which gives you the right to sell the bond at a certain price (strike price) before the option expires. If the bond price falls below the strike price, the option becomes valuable, and you can exercise it or sell it for a profit.

4. **Inverse ETFs**: Some exchange-traded funds (ETFs) are designed to move in the opposite direction of bond prices. By purchasing shares of an inverse bond ETF, you can profit if the bond or an index of bonds falls in value.

5. **Credit Default Swaps (CDS)**: These are more complex financial instruments that act like insurance on bonds. You can buy a CDS contract, which pays off if the bond defaults or its credit rating falls, effectively betting against the bond’s creditworthiness.

6. **Interest Rate Swaps**: You can enter into an interest rate swap where you exchange fixed interest payments for floating rate payments. If interest rates rise, the value of fixed-rate bonds typically falls, and you might benefit from this swap if you’ve agreed to receive fixed rates.

Remember, betting against bonds involves risks, including the potential for significant losses if the bond’s price rises. Additionally, some methods, like short selling, can involve borrowing costs and margin requirements. It’s important to understand the mechanics and risks of each strategy before implementing it. Consulting with a financial advisor or professional is recommended when considering complex investment strategies.