Lets look at a simple example. Picture a 2x4 sitting on top of two sawhorses. (If you've never handled a 2x4 before, step away from the computer right now, head to the lumber yard, and try this.) Imagine pushing on the center of that span. Experience tells us that it will be harder to bend the 2x4 when pushing on the narrow side than when pushing on the wide side. Theory tells us that a plane passing through the 2x4 parallel to one of the "4" wide sides contains more material than a plane parallel to one of the "2" sides. At a very basic level, more material means more material to bend, which means a greater resistance to bending—what we call strength.