Fabric shops often times carry burlap and as stated garden centers use burlap as well. Frankly I prefer cheap loop pile atuo carpet. The main function of the burlap is to keep the foam padding from falling through the springs. In time the burlap will wear out and fall through the anyway. Do yourself a favor and step up and buy a proper pair of hog ring pliers. even if you use them once the job will go much faster and for the novice, safer too. In other words would you rather stain a deck with a one inch brush ...........or a roller.
