There are a few things you can do to train your Lab to become a guard dog. One is to enroll them in obedience classes, which will teach them basic commands that can be used to protect you and your home. You can also teach them specific behaviors that will make them more effective at guarding, such as barking on command or attacking an intruder. Finally, socialization is important for any guard dog, so make sure to expose them to a variety of people and situations from an early age.