Pet door

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.

Another door type, also rigid, may hinge at the top and simply rely on gravity to swing it down to where magnetism may engage to hold it properly closed.

The rigid materials used are often made from plastic for the framing, and for a transparent door element, high density polystyrene, or better such as acrylics like plexiglass.

Human semi-domestication of wildcats dates back to at least 7,500 BC in Cyprus,[4] and the domestic cat was a part of everyday life in grain-dependent ancient Egypt (ca.

In modern times, this function is mostly lost, but in some rural areas, such as Valencia, Spain, and Vaunage, France, farm cat doors and holes (Spanish: gateras, French: chatières) are still common.

[5] In an apparent early modern example of urban legend, the invention of the pet door was attributed to Isaac Newton (1642–1727) in a story (authored anonymously and published in a column of anecdotes in 1893) to the effect that Newton foolishly made a large hole for his adult cat and a small one for her kittens, not realizing the kittens could use the large hole as well.

[7][8] Yet over 60 years earlier, a member of Newton's alma mater Trinity College, one J. M. F. Wright, reported this same story (from an unknown source) in his 1827 memoir, adding: "Whether this account be true or false, indisputably true is it that there are in the door to this day two plugged holes of the proper dimensions for the respective egresses of cat and kitten.

Pet doors are also common between suburban homes and their attached garages, so that pet-related mess (cat box, dog food, etc.)

The advantages of this type of pet door over simpler models are improved weather resistance, and home security against strays and other unwanted animals.

Styles vary, but they are typically made of wooden or metal bars or a wire lattice, and have adjustable widths so that they can be used to span arbitrary entrances, hallways or windows.