Using the large hole punch, punch out twenty circles from the different colors of cardstock. (see photos)
On each circle, draw five lines so that each circle looks like a sand dollar. Use different colored markers to draw the lines on the different colored cardstock circles. (see photos)
Using the small hole punch, punch a hole in the top of each of the colored cardstock circles. (see photos)
Take your piece of yarn and thread one of the cardstock circles onto the yarn. Securely tie the cardstock circle. Repeat with the remaining nineteen cardstock circles, making sure that there is a little space in between each circle. If desired, you may string beads in between the cardstock circles. Once all twenty circles are tied onto the necklace, tie the two ends together. (see photos)
Your necklace is now ready to make any shirt your wearing look fantastic! You can explain to others that each of the twenty sand dollars has five lines so there are one hundred lines on the necklace- a perfect necklace for the hundredth day of school!