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You will need three lengths of 1-1/2 inch (3.8 cm) base ribbon and two lengths of 5/8 inch (1.6 cm) accent ribbon.  Use your two main school colors for the ribbons. Alternatively, you could also use colors that match your homecoming dress. The accent ribbon should be made of an opaque material, like satin. The base ribbon can either be opaque or sheer. For instance, organza ribbon is a relatively easy sheer ribbon to work with.  Measure the circumference of the wearer's leg and add 4 to 5 inches (10 to 13 cm) to that number. Cut two lengths of base ribbon and another of accent ribbon using this measurement. These pieces of ribbon are for the garter itself. Cut 12 inches (30.5 cm) of base ribbon and accent ribbon for the rosette. To prevent the edges from fraying, use an anti-frying craft gel or sew the edges by hand using a zigzag stitch. Use a running stitch to gather the ribbon and sew up the back with a backstitch.  To make a running stitch, allow the needle to run along the edge of the ribbon from the front to the back, and then to the front again. Repeat this pattern for the length of the ribbon. Instead of pulling the thread all the way through, allow the ribbon to gather on the needle, creating a "bunching" effect. Your stitches should be even and about 3/8 inch (1 cm) long. To make a backstitch, pull the thread taut against the ribbon. Push the needle back through to the back, pulling it taut once more. Repeat until the ends are completely sewn together, making your stitches as close together as possible. Alternatively, you could skip the rosette and decorate your garter with a simple bow made from a small strip of your accent ribbon. Repeat the same method used for sewing the base. Attach the accent to the top of the rosette using fabric glue. Sew the accent using a running stitch to gather the ribbon. Sew the ends together with a backstitch. Use your sewing machine to sew the two ribbons together down the center.  Use a thread color that matches your accent ribbon. Pin the accent ribbon to the exact center of your base ribbon before sewing. Sew a straight line down the exact center of both ribbons, fixing them together. Pin the extra length of base fabric to the back of the garter front. Sew the two together with a sewing machine.  Use thread the same color as your base ribbon. Sew both edges of the base ribbon, leaving 1/8 inch (1/3 cm) seam allowance on both sides. Do not sew the rough ends together. You will need to leave these open for the elastic. Attach the elastic to a safety pin and push the pin through the tube, pulling the elastic through so that there is about 1 inch (2.5 cm) of overhang from both ends. The elastic band should be 3/4 inch (1.9 cm) wide. Sew your elastic together by machine using a zigzag stitch to secure it in place. Use a straight stitch to close the open seam of the garter. Before stitching it closed, tuck one end of the garter ribbon into the other to hide the extra elastic and the extra ribbon end. Glue the rosette over the seam. In the center of the rosette, glue a charm or button that personalizes your garter. A good choice for a charm would be a school emblem or school pin. You could also use a sparkly football charm or something that appeals only to your personal interests.

Summary:
Measure out and cut your ribbons. Sew the rosette base by hand. Sew the rosette accent by hand. Attach the accent garter ribbon to your base garter ribbon. Sew the back of the garter on. Feed an elastic band through the ribbon tube. Sew the elastic and close up the garter. Add the final touches. Finished.