https://jsfiddle.net/springgreen11/L2q80bde/
Cat and dog flaps in double-glazed units allow your pets to come and go as they please. They are also great for keeping an eye on your pet whilst you are away from your home. It is possible to install the cat flap inside an existing uPVC or double glazing sealed unit. However, you will need a replacement part with an opening already made. A glazier is able to do this with the right equipment and training. Easy to install Installing a cat flap inside your home is a great option to allow your pet free access to the outdoors without having you