Cat flaps allow your cat to come and go as she pleases. If you have a secure and safe outdoor location for your cat to roam, a cat flap gives her the freedom to go out to do her business and come back to see you whenever she would like. For indoor/outdoor cats, cat flaps represent independence. Putting a cat flap in a plastic door is more difficult than installing a flap in a wood door, but it can be done.
Install a cat flap into plastic doors by following the instructions accompanying the cat flap kit. Most cat flap kits contain a separate set of instructions for plastic.