Scratching at the door is a learnt behaviour dogs and some cats employ when they want to go outside. It's handy to know when your dog needs a trip outside, but it leaves an unsightly mess when the door's paint is marked and clawed away. The most basic method for stopping this is to ignore the behaviour. Reacting when the dog scratches the door teaches her that it's a good thing and she'll continue to scratch. Several strategies discourage scratching, as well as protecting your window and door from scratching's harm.
Hang empty tin cans from a hanger and set it up on the back of your door. The resulting racket when your dog scratches the door might drive him away.
Lock your animal in a crate when she cannot be supervised. Choose a plastic or wire crate for your scratching dog over a soft-sided one.
Place a "doggy doorbell" by the front door if your dog scratches to let you know he has business outside or someone is at the door. The doorbell chimes when the dog presses it with her nose and accomplishes the same task as scratching, but without the damage. This isn't recommended if your dog scratches just because he's excited.
Set a fan near a window or closed door to keep cats away. Felines don't like anything blowing in their face and the fan will keep them from approaching the window. The cat will avoid the window over time, even when the fan is taken away.
Install a pet door, either into a wall or the door, to give animals a way to go outside without your help. Choose a magnetised door that stays closed when not in use to keep drafts out of your home.
Place a clear, protective plastic coating over the base of the door. There are several types on the market that allow an animal to scratch without causing any damage to the door. Just replace the plastic sheet when it becomes too scratched.
Nail a wide piece of wood to the bottom of the door instead of laying clear plastic.
If you rent or don't feel like permanently installing a pet door, take the old door off of the hinges and install a new one. Just put the old one back when you move. Use your judgment, but security usually isn't an issue with pet doors. Most burglars know that if they crawl through a large pet door there's usually a dog of corresponding size on the other side that will not appreciate the intrusion.