Dear WW: I would have said a ruler, except most rulers are too thick and heavy. The sticks paint stores commonly give away to mix paint should work. Half of a cheap yardstick would do. I used to give the kids pieces cut with table saw, when cutting planks to size. Some sticks roar more readily than others, for minute differences in dimensions which I could not discern. The string length is not critical, but roaring does not commence until the contraption is being swung in a circle overhead ;quite rapidly, and the stick is revolving about its long axis.The hole for the string should be centered, and fairly close to the end.