The core material currently put in the backboard differs in the quality of the material by the rank of each maker and a Randoseru.
The Deformation prevention structure of a container changes with ranks of each maker and a Randoseru.
The Deformation prevention structure
It is not rubbed or torn even if a user puts in an intension thing confusedly.
A Randoseru expects that a schoolchild will take good care of a thing.