I would not have been able to keep my high-energy, escape artist Blue Heeler if it weren't for the Tumbo Anti-Shock Trolley Dog Zipline. "Genki" escaped my fenced yard any way possible--over, under or through! I was at my wits end as we have a leash law and having to drive around looking for him was a time-consuming task . I got the 100' zipline and have used it daily for two years with 100% success. Genki can cover the majority of the yard so he gets plenty of exercise and I get plenty of peace of mind! It takes two to install to get it tight. I have retightened it only once since then. So glad I found this product.!