Simple cat door installation, theoretically gives them access to my deck (27 Pics)

This leads to a deck that is cantilevered off the side of the house about 12 feet up so no ground animals can get up and they can't get down to the ground. They've been hanging out on the deck all summer but now that winter's coming I've got to seal the house.

Fitting a board
The cat door

Routing edges to interlock with the window frame