How do you measure the sizes of stones you are looking for to build in your wall? Developing spacial memory is something that is very useful in walling. Identifying shapes and remembering those shapes and sizes we need as we walk through a random pile of stones, can be difficult. Perhaps the last time most of us practiced trying to find and fit different shaped objects into various sized openings was when we played with those coloured wooden educational toys in Kindergarten.
A tape measure is good for measuring and remembering the particular stone you are looking for, but then your hands will not be free to carry more than one stone back to the section of wall you are building unless you put your tape down or stuff it in your pocket. Better to register the size of the stones with your hands. Is it a hand width wide? That's about nine inches, referred to as a 'span'. Perhaps the stone you want is two fists in length. Maybe an elbow plus an outstretched hand? Our hands are our means of measuring. Handy? Yes, and accurate. A tape measure cant match their ability to multitask, as they sort, measure, carry and place. Part of the satisfaction of walling is finding simpler and simpler ways to do the job. Leave it to the hands to come through again with the answer.