https://squareblogs.net/kickwo....rm3/using-upvc-cat-f
Installing a pet flap on your French or Patio doors is a good option if you have a dog or cat. It allows them to enter and exit without you having to open up the door. There are several options for cat flaps made to fit into uPVC, composite, or wooden doors. Some have a four way locking system that can be set to exit only or in-only. Installation Cat flaps are a great way to let your cat into and out of your home without having to open the front door every time. This is particularly beneficial when your cats like to vent