If you've got a cat that likes to jump up on windowsills and lay in the sun, there are a few things you can do to keep them safe. First, make sure your window is securely fastened and won't open unexpectedly. You can also install a pet door or screen so they can't get out onto the ledge. If your cat is determined to get up high, consider putting some cushions or soft fabric down so they don't hurt themselves if they fall.