Answer: Apart from the risk from burglars, there are two problems which can occur with cat doors. One is the problem of draughts, which can be solved by a magnetized strip being fitted to the flap so that a firm push is required before the swing open. The other is the problem of unwanted cats entering the house. Sometimes the come after food; making a practice of not leaving food down may stop this. If your cat is an unsprayed female, males will certainly be attracted when she is in season. Therefore, it is important to have the bolt fitted to the inside of the door which will enable you to keep your cat in, and other out, whenever it is necessary. The absence of any looking device is the disadvantage of another type of cat door which has a circular opening covered by series of overlapping flexible plastic triangles hinged at the circumference.
To pass through, the cat pushes its head at the center, where the apex of all the triangles meet, causing them to bend outward (or inward) and allowing the animal to pass through. The type of flap that required the cat to learn how to lift it deter many strays, but there are also sophisticated types with a battery-operated lock that only open when activated by magnet on the cat’s collar. In theory these allow only resident cat to enter, but there has been a report of a cat wearing this device and learning to stand near the flap, thereby allowing it to be opened, so that its ‘guests’ cab enter before it also passes through!.
