spin ruler / Schreibwaren

Problem:
Paper is too long and your ruler is always too shirt.
Sometimes you really have to draw a stright and long line. But long ruler is hard
to carry at your side all the time.

A convex and a180°-groove make the ruler easy to spin half circle. You can keep drawing the stright line.

It will also incline on the plane naturally.Make your ruler easier to pick up