It appears that the rest of the world has stumbled on to a backstage staple.

http://www.sfgate.com/business/prweb/article/Creative-Safety-Supply-is-Now-Offering-4478937.php

So, I hate hand made signs. They tend to be hard to read and lack necessary clarity that ensures the message is clearly understood.  It reminded me of a good resource for OSHA-compliant sign templates on paper. Not the best solution for long-term marking, but good for that temporary hazard on the occasional piece of scenery that isn't quite finished.

http://www.mysafetysign.com/freepdf/free-safety-signs-pdf-download.aspx