Repairing a tear in an article of clothing is a worthwhile skill to have, as it can not only save you in a pinch, but it prevents you from having to rely on professional seamstresses or garment repair professionals. It also saves you from throwing away or donating an otherwise good pair of clothing too soon. When it comes to trousers, rips most often occur in the knees, seat or crotch since the fabric there is always subject to stretching and tugging against your body. Regardless of where the rip is exactly, you should always use a patch to repair trousers.
Turn your pair of trousers inside out. Cut a patch out of a piece of fabric that is roughly the same colour and made of the same material as your ripped trousers.
Fold the sides of the rip slightly under and pull them gently to each other. Pin them together. Pin the patch to the surrounding area of your trousers.
Sew around the tear with a needle threaded with strong thread or a sewing machine. This is to primarily attach the patch to the sides of the tear. Cut away the excess fabric with a pair of shears.
Turn your trousers right side out and sew a zigzag stitch over the two touching sides of the tear. Use a needle and thread or a sewing machine. Your thread must match the colour of the trousers. Remove all pins.