[Kromm]

Generally, you have to read skill descriptions to learn about possible skill uses. This isn't because we're evil, but because a full list of actions and necessary skills would be as long as Chapter 4! We had space limits, after all. Also, the GM can debase a skill from its controlling attribute to another attribute if he feels like it, creating additional uses that we couldn't begin to enumerate.

Finding secret doors is normally a Per-based Traps roll, since the triggers for traps and those for opening secret doors tend to be one and the same, and since "trap door" vs. "secret door" is largely a semantic difference. However, the GM could certainly allow one to make an Architecture roll (this is a canonical use of the skill; see p. B176). In the right circumstances, even a Per-based Carpentry or Masonry roll should work; after all, it's craftsmen who build these things. But Search is the wrong skill -- it's about finding items hidden on people and in parcels.

I could write a paragraph like the last one for every adventuring task imaginable.