Hi Colin We have 2 eight month old labradoodle sisters. Recently Charlee worked out how to climb the back gate into the park behind us when people walked by with their dogs. We increased the height of the back fence so she just climbed the side fence instead. We were worried she would get hurt or even killed and thought we would have to spend thousands upgrading our fences. My husband came across the Dog Line site and after speaking to someone about it, we decided to give it a go. The system has been incredible. Both pups learnt within minutes where they could and couldn’t go. We have only had to put the collar up to one as they take note of the flags and won’t go past them. We are very grateful to Dog Line as our pups are now safe and happy. Maryanne and Larry