Do not install it on a door that open outside of the other door
I had to perform an exterior installation. My doors are double sliding pocket doors. the first door is on the outside. The only way to install this was exterior. There were no instructions sent to help with the installation of the pet door. The website did have instructions that were not sent with the order. What do you do when the door is locked and the pet comes to the door? ( you better have turned it off or the door will self destruct and grind the crap out of itself.)