Well the term flour sack comes from back in pioneer time, they would buy big sacks of flour for baking in these cotton, tightly woven bags that were sewn shut to keep the flour inside. The women would save those bags, and cut them down into dish towels or even use them for pillow cases, clothing, etc. They are used now a days for baking, cheese making and other uses as well. It's just a plain cotton towel but is smooth, not at all like terrycloth. I use them for bread baking (covering the loaves for the final rise with the towel on top) and also for cheese making/straining, hence not wanting to use terrycloth as the cheese would embed itself into the terrycloth and be impossible to get out, lol. If you do a search on them at walmart.com you will find them there also a company named "mainstays" makes them too.