Reading injection-molded plastic

*Man, this is the stuff. This is the arcane design wisdom. This is the modern urban equivalent of being a Stone Age hunter-gatherer who learns how to read the tracks of tiny lizards.

http://idsamp.wordpress.com/2009/07/20/ejection-mark-on-angled-surface/

"I thought it would be useful to start a series I like to call, "What's That?" where I point out little details on parts and products I see that help designers understand better how they are made and how that might affect their designs… This is