A Hole in the Plate?

In this exhibit, a metal plate has two pipes projecting out. Another small metal plate has been placed a little distance away from the right pipe.

Look through both pipes with both eyes open. While you see the distant scene clearly through the left eye, you right eye sees a non-existent hole in the small plate! One eye registers the hole in the tube on the same part of the retina as the other eye registers the small plate. The brain superposes the two views. This is because our brain has evolved to superpose the views seen by the two eyes that results in perceiving depth or distance of an object.