After landing, a jumper set his brakes and left the rig for a packer. The packer noticed that the jumper had stowed the left brake incorrectly by placing the toggle through the cat’s eye above the metal guide ring, which will not secure the brake line. The brake line would have released during deployment and resulted in a spinning main parachute if the other brake remained stowed. This common packing error is easily preventable by paying attention and stowing your brakes correctly.