Previous research indicates that manipulatives, like base-ten blocks, not necessarily strengthen students’ understanding of numerical place-value and the decimal numeral system. This study takes its starting point in the hypothesis that to create functional teaching situations with base-ten blocks, it is necessary to first know students’ prior understanding of such manipulatives. Therefore, here we present a phenomenographic analysis of students’ understanding how such manipulative material can be used to represent multidigit numbers. The data was collected from individual interviews with 58 students in grade 1 (6-7 years old).We identify six qualitatively different categories of students’ understanding, and, based on these, suggest implications for the design of teaching situations.