If you have being using the cloth shopping bags, I’m sure you have some that have holes in them or a seam has come apart. I repaired a Walmart shopping bag with a piece of denim. I simply took a piece of denim, mainly because it is a heavy fabric, to reinforce the bottom of my bag. First pin the denim into place on the inside of the bag and then sew. After sewing into place, I satin stitched the holes so it would attach to the denim and not continue to become larger holes.