Stone alignments are found worldwide in the archaeological record. As with many archaeological phenomena, these features are often assumed to have been constructed by adults. During ethnoarchaeological fieldwork with Dukha reindeer herders in Khövsgöl Aimag, Mongolia, we observed stone alignments, or “playhouses”, that were constructed by children alongside other stone features that had been constructed by adults. In this paper, we compare stone size and frequency within and between adult- and child-constructed rock alignments. We found that features created by children are characterized by numerous stones of comparatively low weight, while adult features typically have fewer and larger stones. Stones within features created by children also exhibit greater variation in size. We attribute these differences to physical limitations of children and the intended functions of stones in each case. This ethnographic case can serve as a guide for the identification of the authorship of stone features in archaeological contexts.