https://longshots.wiki/wiki/Fi....t_a_Cat_Flap_in_a_UP
A cat flap lets you to allow your pet to roam more freely without the headache of having to let them in and out. It can also make your pet less stressed and prevent them from entering your home when they are not allowed to do so. To install a cat flap inside your door you need to measure from the bottom of their stomachs to the floor and draw a line on the door panel. Check that the line is level using an ad hoc level. 1. The kind of door If you're installing a cat flap into the uPVC door panel or double glazing glass seal