Handyguy Brian installs a dog door on his exterior door on the back of his house. This is a fairly easy install but it always makes you nervous cutting into an external door.
Brian installed a Hale pet door
You can get pet doors for screens, for sliding glass doors and for regular doors. This is a great accessory if you already have an underground dogfence installed.
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Do you want to do a pet door on an interior door? We did an interior pet door video.