It's about 18 inches from the elbow to the tip of the middle finger. Of course, check these dimensions by measuring yourself first. * If you're ever at a loss for a ruler, look in your wallet. Laid out flat, a $1 bill is 6 1/4 inches long. Folded in half, the bill is 3 1/8 inches; folded in half again, it measures almost exactly 1 1/2 inches. Folded lengthwise, the 2 5/8-inch-wide bill gives you a measurement that is very close to 1 1/4 inches. Also, a penny is exactly three-fourths of an inch across. A standard paper clip is 1 1/4 inches long; a giant clip, 1 7/8 inches. * If you don't have a ruler handy, slip a thin rubber band around a straight stick. That way, you'll have a sliding marker that will preserve your last measurement.