This will make you nuts!
1. Look from left to right from top to bottom.
The rod in the middle does not exist.
2. How many, 7 or 10. Count at the top and then at the bottom.
3. Is the door open to inside or outside?
4. Round or square?
5. How many, 3 or 4?
6. Is this just one?
7. Rare construction.
8. The centre beam disappears, look from left to right.
9. 2 or 3?
And NO I don't know how they work, but I think I need new glasses!