[spidey]

A word of caution about invisible fencing - most dogs have at least one motivator which they'll put up with the shock to get to, it may seem like it's working, but I've heard far too many horror stories of dogs escaping from invisible fencing (sometimes after a very long period of use) to ever consider it a truly safe containment system. And invisible fences don't keep other animals or people who could harm your dog out of your yard. I wouldn't rely on it too heavily, it's likely that at some point something is going to matter more to your dog than the shock.