A very short (and possibly poor) instructable on how to make a simple, yet exclusive cat door. I will do my best to answer any questions though....
Step 1: Materials and Assembly
-cheap wood for the inner frame
-nice wood for the outer frame
-a thick piece of leather for the flap/door
The picture pretty much shows the construction. Start with the inner frame by glueing a piece of leather to the top piece of the frame ( ideally glued in a cut out slot made with a router- forgot to take a photo of that-sorry). Use screws to assemble the inner frame.
Oh-and note that the thickness of the inner frame should be the same or slightly less than the door/wall where you mount it.
Step 2: Mounting in Door/wall
Mount the panels to the inner frame using small screws. The panels pressing at the door should hold the cat door in place.