Sashiko is an old Japanese technique used to reinforce and mend clothing. Simply put, it's a lovely way to make something decorative out of a worn-out garment. Cut out a piece of fabric and pin it to the inside of the garment where the hole is. Optionally, mark the front of the garment with a self-erasing marker before you begin. Then stitch up and down with embroidery thread, one row at a time. Make the stitches a few mm longer than the stitches underneath for an attractive cohesion. Feel free to try different patterns than just lines.