https://blogfreely.net/tempers....now0/fitting-a-cat-f
uPVC door panels provide a long-term alternative to composite doors. They are durable, effective and resistant to fire. They are also affordable and easy to maintain. The easiest way to fit a cat flap into a uPVC panel is to buy a replacement double glazed sealed unit with a premade hole for the cat flap. This is safer than cutting a hole into an existing glass panel. UPVC Doors are easy to maintain Unlike traditional wooden doors, uPVC doors don't require frequent painting or sanding. They are also energy-efficient a