we keep the cat’s shitbox in the basement, so i had to cut a hole in the basement door so the cat can go do its business without us having to smell or hear it (our cat poops loud). It is a hollow core door so I need to do something so it doesn’t look like crap. I initially was going to use a few claps but was dreading this as it would be touch to keep the corners square. I found this thing in the corner of a shelf which I forgot I had. I think i ‘inherited’ it when we were dividing up my grandfather’s basement. It is a nylon strap with plastic corners and a screw handle to tighten everything up. it was so easy and the frame came out perfect.