Nearly 70 feet of medium gauge cotton twine, a 3/4 inch ball bearing and an evening of weaving unweaving and reweaving and voila! Still experimenting with weaving slings to particularly-sized projectiles, in this case I had a carry-anywhere pocket-sling in mind, but... I am unsatisfied... it's still a lot of string... I am thinking about trying heavy gauge thread next. These experiments have produced some new knowledge however. I have learned that you must have 12 strands minimum, and I've obtained a feel for how long to make each of the strands in the pocket...the splitting is delicate and I've never been able to construct it correctly the first time... Next stop... a thread string that can hold a marble.