All this lesson needs is an ordinary ruler. Let 'em hold it. Get them to understand that it is a one foot rule. Show them that each foot contains 12 (a dozen) inches. Show them the fractional inch marks. Get them to recognize the differences between, and names of, halves, quarters, eighths, and sixteenths. Have 'em measure some things accurate to a sixteenth. Get 'em to find the center of things, boards, blocks, tin cans, whatever. They do this by measuring to width of the item and then dividing the width in half. Show 'em the trick of halving a fraction by merely doubling the denominator (the downstairs part of the fraction). Show 'em the trick of laying the ruler slant wise so the width measures out to an even number of inches and the center is the center of the ruler reading.
Once upon a time I taught an evening wood shop class for middle school kids. Not one of 'em could read a ruler, let alone use it to find the center of a board.
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