I have two indoor cats that use a litter box in the laundry room. Rather than keep the door open for them, I decided to make a cat door. I've never done this before, but what could be difficult about cutting a hole in the door and framing it? The door needed to be painted anyway.
First I drilled a hole in each corner of where I wanted the cat door to be. I decided to make it in the "panel" of the door so that it would look neater. Then I cut around with my jigsaw to make a square opening.
After that, I made some wood pieces to fit into the sides of the hole I cut. I made grooves in the wood so that it could be held in place with glue and sit a bit inside the door's outer and inner skins.
and then painted turquoise!
I haven't yet put any type of flap on the door, so for now it will stay like this.
* Edited to add: I did put a flap on the door, so the cat could come and go*