– I want to measure the width of a block using a ruler, we’re going to avoid trying to line up the end of the ruler because the end might
be scuffed or damaged. Instead I’ll start it at ten, and looking at the face line up that line with the edge there and then see where this face lines up on that end. Now it doesn’t quite line up with the third line after the 17 and it doesn’t quite
line up with the fourth line after the 17. But it’s closer to the
third than the fourth, so I can say that 17.33 on this end, but I started at 10 on this end. So I have a total width of 7.33 centimeter that’s 73.3 millimeters
for submillimeter accuracy. But better is me to record my number and not tell my lab mates until they’ve made their measurements so that I don’t influence them. And then we take all of those numbers and average them together. And then use that average
as the width of our block.