Close inspection of the WTMetD pathway suggests that the shear mode, where the individual layers slide against each other, significantly shortens the distance between the two next lowenergy hopping sites (the next N or B atom in the neighboring layer), and thus, has a strong effect on the hopping barrier (and even more so on the tunneling probability, which is neglected in this work), as depicted in Figure . Indeed, the barrier for the interlayer shear in h-BN has been found to be rather small, as low as 8 meV and 2 meV, for the shearing between the most stable AA' stacking to the A'B (N over N) and to AB' (B over B), respectively. We estimate that the transition barrier between the layers in static calculations, as shown in Figure , substantially lowers the hopping energy barrier by ~0.5 eV, which is expected to lead to a very small free energy barrier of the overall motion. In conclusion, our simulations suggest that the transport of protons, and also of H atoms, through the interstitial space, follows a shear-mode assisted zigzag hopping pathway.