If you had a dog, you’d want a “dog” door. Or, if you had a cat, you’d want a “cat” door. Since you own both, you’ll want a “pet” door. Right?
Well…. Not exactly. In actual fact what’s important is that the pet door you’re considering be a good fit for the pets you have. So don’t pay any attention to the terms “dog door” or “cat door”. Just measure!
Ok, so what do you measure?
Let’s start with the biggest pet, usually the dog. Open a door wide enough for him to walk through comfortably and measure that width. The flap on the pet door you buy has got to be at least that wide.
Now measure height at the withers or top of his shoulders (he’s going to drop his head to go through). Ideally, the top of the opening would be at that level or as much as 1″ or 2″ higher (especially if your dog is prone to give a little jump as he goes through).
Now think about “step-over”. What’s the highest step-over the cat can manage? Cats are pretty agile; watch her jump onto the bed! Still, when she’s old it won’t be so easy. Same for the dog. So the lower the step-over the better in the long run.
You use the flap height to figure the step-over for the pet door you’re considering. Suppose your dog stands 20″ at the withers. You’re going to mount it so the top of the opening is at 21″. If the flap measures 17″ then the step-over is going to be 4″ which seems reasonable for the cat and is great for the dog.
Now, suppose the flap is only 15″. Not as good is it? The step-over ends up being 6″ which probably works for the dog for now and is less certain for the cat. When they’re old, you’ll be replacing the pet door with a bigger one if you’re still in the same house.
So what if it’s a close call and you aren’t sure? Remember that door open to the right width? Just put some duct tape horizontally to simulate the step-over and flap height and call them both through with a treat. This is the best way to be sure that you’ll be satisfied with the pet door when you receive it.