A field team depended on several local guides during a winter survey. The guides, without whom the team could not have reached the upper valley, knew which paths remained safe after heavy snow. In informal speech, a researcher later described them as “the guides whom we could not have reached the valley without.” Both forms expressed the same underlying relation: the team could not have reached the valley without the guides. A third draft, however, said “the guides whom we could not have reached the valley.” That sentence changed the guides into the object of reached, as if the team had been trying to reach the people rather than the valley. The editor therefore asked the writer to rebuild each relative clause as an ordinary sentence. This test showed whether the relative word filled a verb's object position or the object position of a preposition. The surface location of without could vary, but the relation required by the sentence could not disappear.