Access doors are used as small kitty sized openings so that humans can retrieve a cat from tight spaces like tunnels, stairs, window enclosures, towers, etc. 

Access doors measure 10" W and 12" H. They come with 3 loose assembly clips. 2 latches preinstalled on the door.

All that is needed is for a hole to be cut equal to the size of the door then use the clip assembly pliers to securely hold the included clips in place to serve as the hinges on your new access opening.