Sign up for an Award
Participate with your entry in one of our professional or student awards.Sign up for an award
You are using an outdated browser. Please upgrade your browser to improve your experience.
Mark ruler use the other side of regular rulers as section, is commonly used to void pen stains when drawing multi-color patterns and to keep the whole picture clean. It solves the problem of reversed scale when a regular ruler is turned upside down to maintain the cleanness of a picture.
Zhejiang Normal University