This “cabin” presents a 2 m high and 10,5 cm wide opening.
10.5 cm is the average width of a newborn baby’s head. The skull is man’s largest bone ; when the skull passes, the rest of the body can get through a passage of this width.
When you try to look into this space, in which you’ll never be able to enter, your body hides the only light source behind you that lights the space throug this gap.
The work could also be called “no return” or “one way only”.