The door did not stay closed. 
It is supposed to stay shut with friction along the rim of the box, but it wasn't made tight enough for this. When I crimped the rim of the door a tiny bit, that adjustment made the door stay shut, most of the time. But then the black enamel coating on the box is too thin at the rim and the door scrapes the paint off down to the steel, which will probably rust. 
So making the door hold shut with friction is a bad design, and a catch at the top would be a better idea. Perhaps a plastic stud at the top of the rim of the box  would hold the rim of the door shut.
Thank you for your consideration.