Question: what does 2 by 4 mean?
Answer: "Dimensional" lumber is the general name for framing lumber. ... In the past, when a timber was called a 2x4 [or "two-by-four"], it actually measured 2 inches by 4 inches. Now, most timber is milled and planed to give it a little more of a finished look, and a little more of a consistent size and profile.