Staywell Magnetic 4 Way Locking Classic Cat Flap works with the use of a magnet. When your cat¿s magnetic collar tag comes into contact with the flap, it releases the door and your cat can come and go freely. There is one collar tag included with each unit. Should you wish there is an option to program the flap to enable your cat to come in only, go out only, travel in either direction or it can be locked. This can be very useful for deterring neighbourhood cats.