Cat and dog flaps that are installed in double glazing make it easy for your pets to come and go as they please. These are also great to keep an eye on your pet while you're away. It is possible to put a cat flap into an existing uPVC panel https://windowwithcatflap32955.angelinsblog.com/30211684/installing-a-cat-flap-in-a-upvc-door-cost