The use of manipulatives in upper secondary education is not common, although they hold learning potential in contributing to students' conceptualizing and establishing of relations. In this case study it is investigated how the concept of recursive sequences as a description of growth can be seen in the written reflections from students having engaged in activities with manipulatives like matches and LEGO ® and with only minor teacher interference. The analysis of students' answers is carried out by a combination of Radford's Theory of Objectification and Peirce's Theory of Signs. By interpreting the type of signs, the kind of arguing and the nature of the words used by students in various activities involving manipulatives, it is possible to acquire knowledge of the significance of the manipulatives in students' conceptualizing.