A few days ago my wife and I visited some friends in the country. On one road there was a sign warning of log trucks. If a log cabin is a cabin made of logs, then a log truck is likewise a truck made of logs. Ummm, no … it’s a truck designed to transport logs. In fact, in some parts of the English-speaking world, such as Wikipedia, they are logging trucks, which term I had never consciously encountered. Compare a wooden truck, which is (?toy/model) truck made of wood, and a wood truck, which is a truck designed to transport wood.
English allows the modification of a verb by another verb, which I would call a noun modifier but which Wikipedia calls noun adjuncts and The Cambridge Grammar of the English Language calls nouns as attributive modifiers (p 537). The two nouns can have a wide range of meanings, but neither of those sources has a comprehensive list. Most of the time we have no difficulty understanding the meaning, but there is ample scope for ambiguity, eg a brick factory. (A glass house v a glasshouse (greenhouse) raises another issue, which I won’t go into.)
Some sources classified or classify noun modifiers as adjectives. They’re not – they can’t do adjective-y things like being further modified by very, making comparative or superlative forms or forming adverbs: *a very log truck, *a logger truck than the previous one, *the loggest truck I’ve ever seen, *The truck drove logly.
Never Pure and Rarely Simple 