Pet owners know that it can be a joy to have a dog or cat as a companion, but that there are frustrations as well. For those who let their pet wander freely in the back yard or neighborhood, one annoyance involves a fickle cat or dog who can't make up their mind about whether they want to be inside or outside. During chilly days, a homeowner won't be too keen to keep the door open while waiting for the animal to make a decision.

One way around this issue is to install a pet door within one of your home's doors. This portal can also be put on an interior door or wall, allowing a cat to go to a litter box or food dish in the basement.

While pet doors are convenient, there are also a number of concerns related to them. These include an installation which can potentially be tricky, the need to make the entrance adequate for the pet to use, and worries about security and energy losses.

If you're concerned about making a mistake while cutting a hole in the door or wall, it's better to hire a handyman for the job instead of doing it on your own. Angie's List says you can easily purchase the door on your own, but that a handyman can ensure that the door will be installed correctly.

Make sure the door is properly sized. Hale Pet Door, a company based in Phoenix, Ariz., says it's always better to favor a larger door instead of settling for a door that might be a tighter fit. One common rule for sizing a door is to make sure the top of the door is at the shoulder height of the largest animal which will be using the door; you'll also want to make sure the bottom of the door isn't installed so high that a pet will have to jump to get through it.

When installing the pet door, keep the edge of the opening at least four inches away from the bottom and sides of the door. This will help ensure that the structural strength of the door is not compromised.

Pet doors often come with instructions for installation. In general, you'll want to outline the opening for the door, drill out the corners, and then use a reciprocating saw to cut along the lines.

When installing a pet door in a wall, you'll want to make sure you'll be able to make a clean opening. Find where the studs in the wall are located and aim to place the door between them. Some areas of the home will be more troublesome than others; for example, the bathroom is more likely to have plumbing in the wall.

It can be helpful to open a smaller hole before creating the full opening in the wall. This lets you peer inside the wall to see if there are any pipes, wires, or other obstructions. If you aren't able to place the pet door in its preferred location, the smaller hole will be easier to patch.

Training a pet to use the door usually won't take too long. PetSafe, an electronic pet training products company, says you can put your pet on one side of the door and coax it through from the other.

Security is a common concern with pet doors. After all, you're creating an opening in your door, and the doors necessary for larger dogs can easily allow a person to crawl through.

One solution is to use a lock on the pet door as well as the main door. Ackerman Security, a home security company based in Norcross, Ga., says you just need to get into the habit of activating these locks overnight or when you are out of the home.

You can also upgrade your overall home security system to make your home less vulnerable to intruders. Hale Pet Door says security measures include using a doghouse or other decorative barrier that allows a pet to use the door but bars humans from doing so.

Some homeowners may also worry that an indoor cat may escape through a doggie door. Some doors are electronically controlled, and only activate when a sensor on a dog's collar is nearby. You may also need to use deterrent methods, such as scaring the cat away when they try to exit, to prevent them from using the door.

If you have a lot of wildlife around your home, you may wonder if a squirrel, raccoon, or some other critter will make its way inside. One of the easiest ways to prevent this problem is to keep the pet's food and water away from the pet door so that animals don't come inside to scavenge.

There is also the potential that a pet door can allow cold air to seep in, let air conditioned air out, or allow wind or rain in. Choose a door that forms a tight seal to minimize any energy losses, and use caulk or weather-stripping to further improve the barrier. You may also want to get an energy audit to make sure the pet door is airtight.