Pet Door

A pet door is either spring operated or is hinged door rather than just a flap set into the door or wall or a window. This usually allows dogs, to enter and exit the house without the need of its master to open and close the door for him/her.

Pet doors are usually different from cat doors and are constructed differently and also varies in size. Pet doors are the most convenient ways to let the dog inside and out as they please and reduces the need for trips and also scratching on doors or walls or excerting inside the house.

You need to determine the size of the dog door you'll need. Dog doors come in sizes ranging from small, medium to Large.

You can have a look at the below picture for more information

Also check pet door and cat door.