This was super easy to put together and my cat immediately had no concerns about using it. For those who are concerned about the door letting smell out, I cut a piece of cloth out of an extra curtain, and used a staple gun to staple it to the inside of the door, over the hole. If you do this, make sure the length is just barely long enough to touch the bottom of the opening.  If you make it too long, when the cat comes out, the "curtain" comes out too instead of going back into place.

Pros: Perfect for what I needed!
Cons: None