Sit on the single seated rotor and view through the hole provided in the lower portion of ‘Z’ shaped box.

What did you observe? 
You can see the objects at the higher level easily, which are perpendicular to the top of ‘Z’ shaped box.

The science behind it :
The setup is nothing but a periscope. There are two plane mirrors fixed inside at an inclination of 45 degree at the top and bottom corners. The light rays from the objects are reflected towards the bottom mirror by the top mirror. Consequently the bottom mirror reflects the rays towards our eye. Hence, we are able to see the objects at higher level through the eyepiece.