Pet door sliding doors are commonly known as pet patio doors. This is a simple solution that allows your pet to move freely. Whether you have a dog or a cat they get the freedom to roam around happily. Figuring out how to do a cat or dog door sliding insert is a simple DIY process, don't bother recruiting an expert! With the pet door sliding door you do not need to cut the door or wall. You can insert it very easily. The doors can be any size it depends on your pet's size.