The Petway Door Bracket is used with Petway Pet door. It is especially designed to fit in to the left or right bottom corner of the most standard insect screen doors or insect patio enclosure frames. No cross brace is required when using the Bracket. In most instances it is recommended to fit the Petway Pet Door in the corner directly below the screen door handle. Basic handyman tools are required to install it. 3 sizes to suit small, medium or large Petway Pet Doors.