*** Guide-to-Links ***
WR
WR is used to connect the word "where" to a few verbs like "put".
"Put" usually requires an object plus a prepositional phrase
as a complement; but this prepositional phrase requirement can
be satisfied by the preceding word "where" in questions.

	*I put it

          +-----WR-----+-O-+
	  |            |   |
	Where did you put it

Grammar Documentation Page.