[Usenet: portmanteau, clue + two-by-four] The notional stick with which one whacks an aggressively clueless person. This term derives from a western American folk saying about training a mule “First, you got to hit him with a two-by-four. That's to get his attention.” The clue-by-four is a close relative of the LART. Syn. clue stick. This metaphor is commonly elaborated; your editor once heard a hacker say “I smite you with the great sword Cluebringer!