Pass out rulers to each of your children so that they can examine them.
Point out the numerals on the ruler first. A ruler has numerals 1-12, with each numeral representing a number of inches.
Count the vertical dashes in between any two numbers. If your children count 15 dashes, then they are holding a 1/16-inch ruler. If your children count 7 inches, then they are holding a 1/8-inch ruler.
Measure three different objects against the ruler. For example, measure the length of a pencil, a remote control and a paint brush. To do this place your ruler flat on your work space. Place your object above the ruler making sure the left ends of the object and the ruler are flush.
Compute the measurement. First recognize the inch numeral. For example, if your remote control stretches just past the 5-inch mark, you know that it is at least 5 inches. Count the number of dashes past the 5-inch mark and to the end of the remote control. If you count four dashes on a 1/8-inch ruler, then your final measurement is 5 4/8 inches, which reduces to 5 1/2 inches or 5.5 inches. If you are using a 1/16-inch ruler, then your final measurement is 5 4/16 inches, which reduces to 5 1/4 inches or 5.25 inches.
Apply your measuring skills to making a paper craft item -- such as greeting card that measures 8.5-by-11-inches. You can measure precise parts of the greeting card using the ruler, mass produce it and sell it online or at craft shows.