https://blogfreely.net/bladeto....ilet97/installing-a-
Installing a cat flap in your door is a relatively simple process. You'll need to be aware of a few points prior to getting started. Upvc door panels that have an opening for cats can be installed without needing to cut a hole in your door or wall. Many glass companies provide them with holes already made to fit a pet-door. 1. Safety The cat flaps made from upvc can be easily installed and fitted to a variety of different doors. They are energy-efficient and weatherproof, and have an air-tight seal built-in