I thought this was too simple to post, until two weeks ago. I was at the grocery store, and I handed my reusable shopping bags to the checkout clerk. He said, "I'm glad you remembered; sometimes I forget." I replied that's why the bags live in the back of my car, so I can remember them. Then he asked, "Where did you get these produce bags?" I explained that I ran some yarn through the top of plastic mesh bags, and the one he was holding right then was from the turkey I had cooked for Thanksgiving. After a moment of stunned silence on his part, he said, "That's awesome! High five!"
So in case it's not completely obvious, start with a plastic mesh bag. For me, the larger ones are more useful, and the most plastic-y ones hold up better. I typically re-use these from bags of onions, but this turkey bag is bigger. Weave a long length of yarn over and under at the top until you've woven all the way around; I used a crochet hook for the weaving. Make sure the yarn is larger than you ever expect to open the expandable mesh bag! I have tried plarn and shoelaces, but yarn slides most easily on the bags I've made. So I don't have to weave the yarn in again, I knot the ends together. Store your produce bags with your reusable grocery bags.
