@Joseph Harvey Answer: Because if he bows in the middle of the stalk,, it will break in half. That's why plain (MD) Mouth Drill is tall. Because your hands are back and forth equally, bilaterally. With bowing, the force is unilateral and will break a tall spindle in half. That's why our (MTD) Mouth Toggle Drill & (MBD) Mouth Bow Drill Spindles are shorter.