Circle Cutter / Brieföffner

This compasses is better than
those ordinary ones is because
of it can cut down circles from papers.
Using scissors to cut down circular pieces of paper is always a difficult thing in daily life.
This compasses has a blade on the other end of the needle leg which is hidden for safty
when it not being used.
Normally we use the needle leg as the center and use the pencil leg to draw a circle,
and when we need to cut down a circle, we just need to reverse the needle leg and use
the pencil leg as the center so when the blade drawed a circle, a pieces of circle will be
cut down from the paper.