This optical illusion uses 3D overlap, perspective angles and shading to create quite a puzzle. The rods coming out towards you from the large block in the center really stick straight out and do not touch anything. They appear, in this puzzle, to connect with the two up and down posts because the perspective angles on their ends makes them look like they do. They appear to overlap and continue right through the bottom of the posts.
The shading of the different parts causes us to group them together, which supports this optical illusion.