This article presents data gathered from an investigation which focused on the experiences children have with measurement in the early years of schooling. The focus of this present article is children's understandings of length at this early stage. 32 children aged 4 to 6 years at an Australian primary school were asked to draw a ruler and describe their drawing, once in February at the beginning of school, and again in November towards the end of their first year of school. The drawings and their accompanying descriptions are classified within a matrix which, informed by Bronfenbrenner's ecological theory and literature regarding the development of length concepts, considers conceptual understanding and contextual richness. The responses revealed that children have a good understanding of length at the start of school, but that as their ability to contextualise develops so too does their conceptual understanding. This article suggests that participation in tasks such as these allows children to create their own understandings of length in meaningful ways. Additionally, the task and it's matrix of analysis provide an assessment strategy for identifying children's understandings about length and the contexts in which these understandings develop.