The Internet's Pet Door Authority

Determine the Type of Pet Door you require
You will see that pet doors are basically broken down into two major classes of doors.  That would be Manual (Flap design) or Electronic (Controlled access).  The Manual pet doors (Specifically the dual flap doors) are your better sealing and insulating pet doors.  Single flap doors are used in situations where an insulating effect is not warranted.  Electronic Pet doors control the access of pets and in a few doors are designed to keep out other animals.  Pay close attention to the notes and descriptions we have on these doors as this controlling action does vary.  Most Dog owners find that they do not have issues with other animals that enter a pet opening.  Dogs in particular are territorial and do not entertain sharing their pet door.  All pet doors will lock or have a slide in security locking panel to close off the pet opening.  Most will lock off the dog door at night or when away.

Where Should I Install a Pet Door?
Pet doors are made to be installed just about anywhere.  This ranges from the traditional wall mount or door mounts to window pet doors and patio sliding glass doors.  Everyone's home is different and if you can prioritize the best places that you could use a dog or pet door then you can quickly see what doors will work in those situations.

Make Sure you have Selected the Appropriate Size Pet Door for your Pet(s).
It seems to often that when we speak with customers about the size of pet door they are considering, we find that many times it would be too small.  You will want to keep the size your pet could attain, the type of breed (Arthritis and physical problems are more prevalent in some breeds versus others) and especially is the outside ground is on the same plane as your interior flooring. 
As a rule of thumb:  the pet opening should be mounted so that the top of the opening is 1.5-2" higher than the pets shoulders and low enough to the ground so their legs will not scrape and allow for easy access as they age.

-