We have two Border Collies, a half acre and no fence. We walked the perimeter with the dogs a few times and now they stop at the border. We have a chain outside the back door so first thing in the morning I can put them out to do their business without having to worry about a skunk being out there somewhere in the dark. They are on the chain for maybe 10 minutes each in the morning and then any other time we are outside with them at all times! Even when the tennis ball goes into the neighbours yard they stop at the edge of the property and wait for me to retrieve the ball! They say Border Collies are easy to train and now I believe it.