A cat flap is a hole that's in your door that enables your cat to come and go as they please. This design isn't extremely secure and could give access to burglars. You may also think about upgrading to an automated or lockable model that comes with more security features. https://doorswithcatflap21474.blogzag.com/74862874/adding-a-cat-flap-to-your-bifold-doors