If you've pulled out your favourite winter sweater only to find a moth has put a hole in the wool, you know how aggravating it can be. But you don't have to throw it out. You can fix the sweater if the damage isn't extensive. It may not look brand new anymore, but it still will be comfortable and fine to wear.
Place the damaged part of the knit wool on a table and flatten it so you can see which threads have been chewed. Don't pull on the garment or the threads may unravel more and cause additional damage. Flatten it gently.
Remove any fluff or broken threads that are in the way. You should see the ends of at least two ends, maybe more. These threads must be secured so they won't unravel anymore.
Tie 6 inches of new yarn to an existing broken end with a simple knot. When you pull on the old yarn, be careful to not unravel any more stitches than absolutely necessary. Tie another 6-inch section of yarn onto the other end of broken yarn and lay it back on top of the garment so it is out of your way.
Poke the crochet hook through the first stitch closest to the new yarn and pull the new yarn through the stitch. While you are doing this, hold the other stitches with your other hand so they don't get pulled and unravel. Continue to the next stitch and pull new yarn through and then do a simple slip stitch before moving on to the next one.
Go around the hole, securing each stitch until there are no loose ones left. Cut the yarn so there is only about 6 inches left on the crochet hook and push it through so it is on the underside of the garment. Pull the 6-inch section of yarn that you set aside earlier in Step 3 through to the inside.
Pull the yarn on the crochet hook through the last loop remaining on the hook and set the hook aside. Tie the two pieces of yarn together with a simple knot close to the garment. Leave about an inch of yarn and trim the rest off. Turn the garment rightside out and wear as normal.
Work from the inside of the garment for a neater finish. Knot off any loose threads if there are more than two.