It was quite easy to make the periscope. But I need to see at the end of the movie what to do 
I have no idea how it should look like. But after that it took me few minutes.
I did mine from 3 cubes. Then I deleted vertices from the upper cube and from the down one. I left two side which look like L. Then I selected 3 to make triangle face on both sides and a plane face. Both by filling with F. After that I joined all three objects and move them up to make the base on 0 position.
