To mend a rip or tear in jeans, you'll need to stitch the fabric back together. Start by using a needle and thread to sew the two sides of the fabric together. If the rip is large, consider using a patch of fabric to reinforce the area before stitching. If the rip is small, an iron-on patch may be enough to repair the damaged area. With patience and some basic sewing knowledge, you can make your jeans look as good as new.