Dog House Door Flap Diy . 7 diy dog door plans 1. We attached a frame and an interior flap both on the outside and inside of the door. DIY Dog Door for French Door Window Panes Howchoo from howchoo.com A box cutter and scissors. A complete guide to vents for dog houses including diy instructions and best solutions. The metal roof stands up to the elements, while the small wooden overhang provides a touch of protection from rain that may try to whip inside.