Eye / invisible objects

Im sure there is somewhere thing what tells about this but i just cant find it so please give me some link.
So i want to know how I get the secret doorways and these things what I can see when I get the eye power upp.
Sorry for waste of your time!

Anything in Bank Ghost can only be seen/walked through with the eye. Object 5 is a wall. If you put object 17 down on a layer 3 tile you can walk through it with the eye. Objects 18-21 are just decor, but they're usually used to show hidden passageways.

Thank you.