PetSafe In-Ground Fence pet containment systems provide your pet with freedom and safety while spending a fraction of the cost of traditional fencing. It's easy to install, reliable, and safe. With proper training it is a very effective way to keep your dog safely in your yard. It works through the lightweight collar your dog wears. The collar picks up the signal from the buried wire and alerts your pet he has reached the boundary. The in-ground boundary wire is sold separately so that you can purchase the gauge best for your yard.