An invisible fence might seem like an ingenious, low-cost solution, but invisible fences, on the whole, have a lot of problems. For one, they only keep your pet in - they don't keep other animals out. Shock collars can also potentially cause injury to your pet, and even when they're not physically injurious, they can still cause your pet to become more fearful, reactive, and aggressive. A physical barrier not only reliably keeps your pet in your yard without using painful or anxiety-inducing deterrents, but it also keeps intruders out, thereby protecting your pet at all times.