Planking is the act of laying face down on an object. It can be seen in the cold open of the season 8 premiere, The List. It was a trend popular in 2008, making all the more funny that it was shown in this 2011 episode. In the episode, Oscar spots Erin lying face down on a parking divider. As he explains, planking is a "very stupid and dangerous trend. Basically, you lie like a plank in weird places. That’s it. Sometimes you get run over. Welcome to the Internet." As Erin explains, "planking is one of those things where you either get it or you don’t". Erin explains that she doesn't get it but that she is excited to be a part of it. Later in the episode, Andy explains that, as manager, he made Dwight his enforcer, and instructed him to do whatever he could to stop people from planking. He does, doing everything in his power to stop people from planking, even spraying them with fire hydrants and dropping books onto them.
Dwight enforcing planking restrictions in "The List".