We report the experimental and theoretical study of boron nitride nanotube (BNNT) torsional mechanics. We show that BNNTs exhibit a much stronger mechanical interlayer coupling than carbon nanotubes (CNTs). This feature makes BNNTs up to one order of magnitude stiffer and stronger than CNTs. We attribute this interlayer locking to the faceted nature of BNNTs, arising from the polarity of the B-N bond. This property makes BNNTs superior candidates to replace CNTs in nanoelectromechanical systems (NEMS), fibers, and nanocomposites.