https://yamcode.com/cat-flap-double-glazing-35
Installing a pet flap on your French or patio doors is a great idea if you own a dog or cat. It allows them to go into and out without having to open the door. There are a myriad of cat flaps available to fit uPVC composite or wooden doors. Some even come with a four-way locking system that can be set to exit only by entering only, or open. Installation Cat flaps can be an excellent method of letting your cat go in and out of the house without having to open the door every time. This is particularly beneficial for cats who are keen to get