Whether right- and left-handedness are defined as a function of individual tasks or represent general categories across tasks has been long debated. However, the literature on handedness primarily concerns industrialized societies in which manual work has been extensively automated, and the majority of individuals in those countries do not use their arms and hands intensively for highly specialized tasks on an everyday basis. Thus, the question remains whether results from those countries regarding handedness are transferable to countries where the majority of individuals are still exploiting their lateralized skills. Here, we sampled 506 individuals from 143 locations on the islands of Flores and Adonara, Indonesia, to assess their hand preference for and hand performance on several tasks in order to evaluate, in a non-industrialized country, the level of manual specialization and the relevance of right- or left-handedness as general categories. Generalized-declared handedness was consistent with task-declared handedness across 10 specific tasks and with a measure of strength and a measure of skilfulness, suggesting that general handedness is a valid concept. This hand specialization for tasks is discussed in the context of intense and daily tool use in this agricultural society.