Do you have cats? If you do, you'll notice that they spend a significant amount of time looking out the windows in your home. This is normal behaviour for a cat; they love spending time looking at things going on outside the house. The problem, however, is that their choice of perch (the window) is very unsafe. When they perch on the window sill, they are usually somewhat unstable, and there's always the risk that a strong wind could blow and knock them off.
While you can't prevent your cats from climbing the window, what you can do is make it safer for them. This wooden window perch is precisely what you need. When you install this device on your window, your cat will be perfectly comfortable. So you won't need to be worried about their safety.