How to find lab secret passages

Sometimes I swear I feel something suspicious behind a wall or one of those iron maidens, how do people check for those? Or do their name show up when you mouse over it?

yes, you can click them if there is something hidden, if you explore the Lab a bit you also notice that most elements where hidden passages (from area to area) 'could' be, are on the minimap
on the whole Lab for one day they shift a bit within the area the are in for example i got some where a hidden passage was left from the way to the next area and on the next try (on the same day) it was right from the way to the next area
depending on how the layout is and to what other area the passage leads it makes sometimes no sence to take them (run by run)

passages to hidden rooms is a whole other story, usually there is a switch near, after finding some you remember the layout of the enviorment so you see this two walls and know there is a swich near.