Pet door

A pet door or pet flap (also referred to in more specific terms, such as cat flap, cat door, dog door, or doggie door) is a small portal in a wall, window or human door to allow pets to enter and exit a house (or other structure) on their own without needing a person to open the door. Originally simple holes, the modern form is a hinged and often spring-loaded panel or flexible flap, and some are electronically controlled. They offer a degree of protection against wind, rain, and larger-bodied intruders entering the dwelling. Similar hatches can let dogs through fences at stiles. A related concept is the pet gate, which is easy for humans to open but acts as a secure pet barrier, as well as innovative automated left- or right-handed pet doors.

A pet door is found to be convenient by many owners of companion animals, especially dogs and cats, because it lets the pets come and go as they please, reducing the need for pet-owners to let or take the pet outside manually, and curtailing unwanted behaviour such as loud vocalisation to be let outside, scratching on doors or walls, and (especially in the case of dogs) excreting in the house. They also help ensure that a pet left outdoors can safely get back in the house in the case of inclement weather.

The simplest type are bottom-weighted flaps hung from the top of the opening, which swing shut on their own, but may be spring-aided to increase wind resistance. These flaps often feature magnets around the edges to help keep the door closed against weather and wind. Some doors have side-mounted hinges and more door-like operation—like a saloon door. These pet doors usually have a spring or other contrivance to force their closure after the pet has gone through. Instead of a rubber flap, saloon style doors are often made from plastic, acrylic, or plexiglas, and the panels are fitted with weatherseal to help keep weather outside.

Another common feature is an adjustable catch to restrict the opening of the device to either one direction or the other; for example, to allow the pet to come in for the night, but not go out again until the owner releases the catch the next morning. Some pets, mostly cats with their retractile claws and flexible paws, learn to circumvent one-way pet doors, especially the "flap-within-flap" design.

Most also have a locking mechanism of some kind, and can be closed off by sliding a rigid plate into parallel rails on the left and right of the interior side of the pet door to close it off, e.g. during bad weather or when the owners are travelling with their pets.

Pet doors are generally designed to be safe for any pet. The panels are often designed with soft vinyl that does not trap or injure the animal. Cheap, easily replaceable pet doors are made from plastic and as such may not always be robust enough for large, boisterous pets.

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Wikipedia