In early childhood, young children frequently engage in object-oriented play. According to cultural-historical activity theory, object-oriented play provides children with opportunities to learn about the characteristics and cultural applications of objects and materials. These characteristics are referred to as rules or affordances of objects and materials. To date, what kind of rules children explore and follow, and how they do so, has not been extensively studied, even though the understanding of children's learning in object-oriented play is important for early childhood education. In the current explorative study, we analysed how six children aged between two and four years explore, follow, and impose rules during a 10-minute play activity in which they were presented with a fixed set of objects (e.g. oddly shaped blocks, boxes, abstract shaped puppets, etc.). Thematic analysis of video-observations revealed two themes: (1) children explore, follow and impose different types of rules using different strategies, increasing in complexity with age; and (2) children explore, follow or impose rules by various forms of repetition, with older children showing longer and more complex forms of repetition. In the discussion, these themes were interpreted using CHAT.