Here's why:
* Narrow passageway: This phrase has no single-word homophone.
* Put into horizontal position: This is a phrase, not a single word. The closest single-word homophone to the action of "put into horizontal position" might be "lay" (as in "lay down"), but that doesn't encompass the "horizontal" aspect.
However, we can play with words a bit!
* "Lay" could be a homophone for "lay" (as in lay down a narrow passageway).
* "Lie" (as in "lie down") could be a homophone for "lie" (as in "the narrow passageway lies hidden").
These are creative interpretations of the prompt, but they don't perfectly fit the original meaning.