  Graphene nanoribbons can be folded into a double layer system keeping the two
layers decoupled. In the Quantum Hall regime folds behave as a new type of Hall
bar edge. We show that the symmetry properties of the zero Landau level in
metallic nanoribbons dictate that the zero energy edge states traversing a fold
are perfectly transmitted onto the opposite layer. This result is valid
irrespective of fold geometry, magnetic field strength and crystallographic
orientation of the nanoribbon. Backscattering suppression on the N=0 Hall
plateau is ultimately due to the orthogonality of forward and backward
channels, much like in the Klein paradox.
