https://historydb.date/wiki/Through_Wall_Cat_Flap
Your cat and you can both benefit from having a cat flap in your bifold door. It also helps to prevent extreme heat or cold from entering your home. First, you need to take measurements of your pet to determine the right size door flap you need. This will allow you create a cat flap hole that is of the right size. Outdoor Access Even those with basic DIY skills can manage to install a cat flap to an exterior back door. This will save you the cost and hassle of contacting an experienced joiner, carpenter or handyman to carry out the job