With this jig, I can buy plain dowel rods and flute them myself. To make one, take a block of 1-1⁄2"-thick scrap that measures 3-1⁄2" square. Cut it into an octagon shape and bore a 3/8"- or 1/2"-diameter hole through the center (depending on the dowels you plan to use with the jig). Then drill a 1/8"-diameter hole, centered on each of the flats, going through to the dowel hole. Drive a 1-5⁄8" drywall screw into each hole until just the tips of the screws protrude into the dowel hole. That’s it! Pounding a dowel through the hole cuts eight flutes in a single pass. Use a length of spare dowel to drive the end the rest of the way through. Then, give the dowel a little twist and cut eight more flutes with another pass.