Chalk
From Not the Rensselaer Wiki
A number of different students have been responsible for producing temporary chalk drawings around campus.The Chalking Efforts
A large batch of the drawings done by Maureen Duffy that were accompanied by a link to http://chalk.rpi.dhs.org/ are now available at http://www.poundrpi.net/chalk/.
Cory McWilliams has done several which are available at http://acm.cs.rpi.edu/~cory/projects/Chalk/.
Students calling themselves the Chalk Club have contributed a number of original yet confusing sidewalk chalk contributions.
About Chalking
Chalk drawing on campus is often done with a simple bucket of Crayola sidewalk chalk and some charcoal. Popular subjects are cartoon, comic, anime, and video game characters.
The student handbook actually has a sign policy which forbids chalking on campus in section III E.
Signs may be mounted on bulletin boards only with thumbtacks and staples. Nails, duct tape, string, chalk, adhesive-backed signs (bumper sticker type), and direct application of paint to any surface are prohibited.
However, given that chalk drawings tend to last only a short time, depending on foot traffic and rainfall, it is a rare expression of art on a technical campus, and it has been done more often for fun and entertainment than advertising, it seems to have become a well-accepted practice.

