A wooden block among the bricks
This image is fairly easy to understand and does not require much concentration to guess what the flaw is. It appears as if the workers bought too few bricks for the construction of this building, so they made the drastic decision to use a perfectly shaped piece of wood to replace the missing brick.
They probably thought that no one would notice a single brick missing from the entire wall. But we definitely do. Let’s hope that the wooden piece can withstand the pressure of the real bricks on top of it and that the finished wall will be able to stand in place without breaking and causing any undesired accident.