Cut two 18 inch lengths of nylon webbing. You can find webbing in the ribbon section of any sewing or fabric store. Stitch the webbing handles into place on the top of the bag as shown, centering them between the side seams.
You can substitute ribbon or fused plastic for the webbing, if desired.
Use the finished bag as desired — it is strong enough to use as a grocery store or library tote, thanks to the multiple layers of fused plastic.