Yes, if you mean a washcloth on the bottom of the pot, not the jar. Anything will work within reason. Washcloth, cake rack, canning jar lids, a few spoons, an official canning rack, etc. Point is to keep the jar from touching the bottom of the pan.
I use a round cake-cooling rack to keep my jars from touching the bottom of my pot. I own 2 different sizes- one that's about 9" round and fits in my large soup pot, and a smaller one that fits in my 2 qt. stockpot. I set my jars right onto the rack.