I subscribe to the This Old House email newsletter. My old house philosophy differs vastly from theirs. However, I will admit that they do know their stuff and generally I find the articles very interesting (even if not applicable to my house).
In today's newsletter there was a little piece of trivia that I loved. I'm sure I will be able to pull up this piece of info. at sometime in the future and impress someone.
Ever wonder why that hook on the end of a tape measure isn't fixed in position? It wiggles on its rivets to make up for the hook's thickness. Push the tip against something for an inside measurement, and the hook is included in the reading; hook it on the end of a piece for an outside measure, and the resulting gap equals the space the hook would take up. But if the hook leaves you guessing when you’re measuring short distances, line up the 1-inch mark at the start, then deduct that extra inch from the final measurement.