It’s a longer distance from the corner of a square or rectangle to its center than it is from a parallel edge.
That’s why when you tip up an 8-foot basement wall frame into an 8-foot floor-to-ceiling opening, it doesn’t fit—its longer from corner to corner than it is from plate to plate. It’s the same reason a drawer doesn’t fit in any other way besides straight.
Next time you spot a house with a hip roof, the hip’s “run” is 17 inches for the same reason as opposed to a typical rafter’s 12-inch run.
