'Essi fecero un muro' vs. 'Essi fecero muro': on the surface, these Italian sentences differ only for the presence of an article before the post-verbal noun (PVN) 'muro', literally 'wall'. Despite this minor divergence, their VPs vary greatly in meaning: the former can be rendered as 'They built a wall', the latter as 'They put up resistance'. In Italian, many other nouns behave as 'muro' does above. The meanings come from distinct structures: PVNs preceded by an article are direct objects. Bare PVNs, at times the very same noun, can either pass tests for direct object-hood or show distinct syntactic ties with the verb.
Mirto, I.M. (2009). Changes of meaning due to changes of articles: A study of singular count nouns in post-verbal position in Italian. In C.S.e.a. Clausen (a cura di), Arena Romanistica (pp. 254-264). Bergen : University of Bergen.