Pet access flap for screen doors provides instant indoor or outdoor 2-way access for cats and smaller dogs. The pet door is hinge-free and swings open or closed as pets enter or exit through an access opening. Installation is quick and easy with the screen door plastic snap-on design, and the pet door can be locked shut with included plastic pegs. Ideal for use with screened patio doors, storm doors, or windows. To ensure the pet door will work as intended, please measure pets to ensure they can comfortably fit through the 7.75" wide by 9.5" high screen opening. For high traffic screen doors that tend to slam shut often, we recommended to apply a little glue to each side of the pet flap to ensure a firm long-lasting grip over time.