It is recommended to hire an professional to install a cat-flap inside your home. DIY projects usually result in poorly-fitted pet flaps that can let in draughts or increase energy costs. SheffLOCK can install cat flaps on all types of doors, including wood, glass, uPVC composites and even external walls. https://cat-flap-fitters36643.blogoscience.com/36926757/using-a-cat-flap-in-bifold-doors