In this article, I discuss children's design of mathematical represent
ations on paper, asking how material displays are constructed and tran
sformed in activity. I show that (a) the design of displays during pro
blem solving shapes one's mathematical activity and sense making in cr
ucial ways, and (b) knowledge of mathematical representations is not s
imply recalled and applied to problem solving but also emerges (whethe
r constructed anew or not) out of one's interactions with the social a
nd material settings of activity. A detailed characterization of stude
nt-designed tables of values to solve problems about linear functions
is also presented.