Hi Charles. The filters I buy have angles edges and they stack sort of nested like so the profile is not much higher. You know Charles, you are right, its only the ones at Home depot and WM in my area that I have ever seen that are made that way.
They are actually pretty strong on their own( for what they are), but I do use two. You probably have a vertical draft unit with the filter on the side or bottom of the blower compartment. I have an attic furnace and I change my filter form a drop down return air grille in the hall, so I have a bit more space and installation flexibility than if you had to slide them into a slot. I just discovered this method when I first bought a pack of them last year.who knows maybe they wont even make them next year.Good catch Charles and I hope I was able to fix that confusion.