It works. My dog was jumping up over my brand new fence, at the high point of 7ft! Amazing to say the least, we couldn't keep her in the yard, tried several other options but nothing would do it. This was my last resort, and by god it worked the 1st day.I tested on my arm up to a level 3 and deemed that to be enough shock to startle me, so 3 is what the dog gets. Hadn't had to got to level 4 yet.Worth it! And read the instructions. Twisting of the wire is great to make the Hotwire deactivated. Drill came in hand for that.