Keeps my little terrier in the yard. He is a fence digger, and this keeps him off the fence. I don't always use it, and wondered how well it really worked. The other day there were some pit bulls running my fence line, and my dog was running back and forth along the fence with them. Fearing for his safety, I turned the fence on. My dog headed straight to the middle of the property and away from the fence. Other dogs went away once they realized they could not get to him, and all was right in the world again.