Installing a cat door can end your days as a door opener. Putting one in as a gateway to a screened porch is a great way to give your cat safe access to the smells and sounds of the great (and dangerous) outdoors.

The basic cat door has a flexible plastic flap that opens as your cat pushes on it and seals shut again with gravity -- and sometimes magnets -- to keep the heat, cold and wind out after he's passed through. Although these flaps are fine for warmer climes, they may be a little drafty in areas with more severe winters. Be sure to check out window models such as those from LetMeowt.com.

To teach your cat to use the door, tape the flap up securely for a few days so that he comes to appreciate the fact that he can conveniently come and go on his own schedule through this magic portal. (And I do mean securely. If your cat gets clobbered by the flap, it'll take a long time to coax him near it again.)

Then put the flap down and put a little butter or margarine on the bottom edge of the flap and encourage him with tasty treats and praise from the other side. You can also drag toys on a string through, encouraging him to chase them.

Repeat in very short intervals over the course of several days and your cat will get the hang of it, sure enough. If you have another cat who already knows how to use the cat door, you usually don't need to do anything. Your new cat or kitten will learn from the other cat -- or even the dog.