https://blogfreely.net/bucketw....asp1/choosing-cat-fl
Introduce your cat to the flap before it's set up so they can be familiar with the size and shape. Unlock the flap and let your cat explore it from every angle. Make sure that the cutout is square and even. Mark the screw holes on your door and align them with the opening for the cat flap - the distance between the edges should be equal. Preparation Installing a cat flap inside your home can be beneficial to the well-being and health of your pet. This is because it will allow them to move freely between indoors and outside