\input zb-basic \input zb-matheduc \iteman{ZMATH 2014b.00296} \itemau{Teppo, Anne; van den Heuvel-Panhuizen, Marja} \itemti{Visual representations as objects of analysis: the number line as an example.} \itemso{ZDM, Int. J. Math. Educ. 46, No. 1, 45-58 (2014).} \itemab Summary: Our paper examines the representational nature of number lines as they are used in instructional tasks. The examination is informed by a so-called mathedidactical analysis of the number line as a tool used in teaching students mathematics. This analysis led to the identification of a family of number line models, based on visual aspects of number lines each reflecting different forms and functions. In the article, number line tasks are unpacked to illustrate the visual representational components of particular number line models. We illuminate how these components of the models provide tools to locate whole numbers and integers, operate with them, and facilitate reasoning and understanding of underlying mathematical concepts. \itemrv{~} \itemcc{D40 F20 D20} \itemut{number line; number line tasks; representational aspects of number line; subject-related analysis; number line as tool; number line as structural reference context} \itemli{doi:10.1007/s11858-013-0518-2} \end