If you are planning to install a cat flap inside your home, it's best to work with an expert tradesperson. DIY projects usually result in a poorly-fitted pet flap which allow drafts and cause higher energy bills. SheffLOCK can be installed as a cat flap on all kinds of doors, https://cat-flap-installation-nea55439.yomoblog.com/37137340/using-a-cat-flap-in-bifold-doors