Those concerned about security should consider electronic pet doors. These are are controlled by Infra-Red "keys," which your pet wears on his collar to activate the system. The units generally come with one collar key, and additional ones may be purchased. These smart systems don't raise the door if your pet just walks by or if it lies in front of the door. Better yet, electronic units keep neighborhood pets and intruders (both human and raccoon) out, while keeping babies and indoor pets inside. Electronic doors are also weatherproof, meaning they can't be blown open by gusts since these doors slide instead of flap. Some electronic ones, especially those for smaller pets, function in only one direction, so keep this in mind while shopping.

For those who rent or don't want to alter their home, an instant-install "patio panel" door may be ideal. These pet doors slip into the frame of your sliding glass door and are sealed at the top to conserve energy bills, but allow your pets freedom. Installation of patio panel units is simple, and they can move with you if you relocate. Another option is an automatic sliding door mechanism that retrofits your existing sliding glass doors. This style is great for people too, particularly those with arthritis or other physical disabilities. Automatic whole-door systems can be operated by collar keys or a numeric keypad that allows your family safe entry through their full-size door.

All models allow the owner to lock the door flap, and many can be set to let pets inside only or outside only. Those Dog doors that run on batteries won't fail your pet during a power outage. Many newer electronic units have been designed for installation into metal doors, which interferes with some older models. It'll only take a couple hours to a few days to train your pet the wonders of their new Gun Dog House Door "Extreme Use" Easy "Big Dog" Pet Door.

When buying any model, you'll need to know the size opening required by your pet. The flap should be at least as tall as your pet's shoulders, and the "rise" low enough for him to walk over comfortably, even when he's older. The minimum width is, of course, the width of your pet. You can often match the frame to your existing trim, too. The frames of most doors are rustproof, low-maintenance aluminum, but plastic and wood are available. For patio panel or window models, choose between single-pane and double-pane glass, and measure the existing opening carefully. Depending upon your mechanical expertise, you may decide to hire a professional to install your new unit, though most pet doors are designed for owner installation.