Print 2 copies of the included .stl file. I printed it in ABS at .2mm layer height with 20% infill. No support is needed. Glue the mirror to the inside of the printed parts. I used a hot glue gun. Cut a section of vinyl gutter. I used a piece about 18" long. It's up to you how long of a periscope you want to make. Glue the printed pieces to the gutter section. Be sure to glue them facing opposite directions. Again, I used a hot glue gun.