It is possible to install an apron flap inside the upvc panel, or even a double glazing sealed unit. The best option would be to install the glass pane from scratch using a pre-made hole. Follow the instructions provided with the kit. Make sure the shape you've drawn (be it https://cat-flap-fitting-near-me57875.worldblogged.com/36610523/cat-flap-cost-near-me