Explain xkcd: It's 'cause you're dumb.
There's also the right hand rule on urban dictionary, although it's applied slightly differently, and it only has one input parameter. Davidy22 (talk) 03:44, 30 October 2012 (UTC)
I expanded the explanation to cover the erection joke. 22.214.171.124 02:12, 27 August 2013 (UTC)