Device One
      

Periscopes work on the principle of letting the viewer see a view or angle he is unable to see
 
 
 
 
 
 
 
 
 
 

Device Two

The movie Sliding Doors (Directed by Peter Howitt, 1998) portrays the notion of alternate realities that diverge at a single  moment based on a series of choices.

The sliding frames in the second device could allow the viewer to choose various viewing realities based on which slides are in or out of the mainframe

Frame 4

Frame 4 of the sliding frames acts as blinds do to control the amount the view visible to the user
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Device Three and Six

Device Three serves to visually block off the surroundings allowing the viewer  to focus on the view through the device, similar to blinds on a horse!

Device Six implements multiple mirrors creating a fragmented view as seen in the famous mirror scene in Bruce Lee's Enter the Dragon