Sure we do it every day in all sorts of ways, but just how good are you at "eyeballing it"? Do your shelves tell one story of woeful inaccuracy that you feel must be corrected?
This quiz on how well you give the eye to creating parallelograms, right angles, finding a point equidistant from the edges and more gives you three rounds of opportunities to see if your precision matches your swagger.
In the end, how did you measure up? (First attempt for me: 12! Not terrible).