Cat Proof Fence Extension is an addon to your existing fence. Your fences will need to be at least 4ft high at minimum, the ideal height is 5-6 ft, any gates need to be the same height as the fence. If you have a garden shed in a corner the netting can be made to come around the front instead of the back.
 
The netting is angled back onto your property, and being a netting it is quite flimsy to try and hang on to. This is enough to stop any cat from climbing over the top.