  We show how the local approximation of astrophysical discs, which is the
basis for the well known model of the shearing box, can be used to study many
aspects of the dynamics of warped discs. In the local model, inclination of the
orbit of a test particle with respect to the reference orbit corresponds to a
vertical oscillation of the particle at the orbital frequency. Warping of a
disc corresponds to a locally axisymmetric corrugation of the midplane of the
disc that oscillates vertically at the orbital frequency, while evolution of
the warp corresponds to a modulation of the complex amplitude of the vertical
oscillation. We derive a conservation law for this amplitude that is the local
equivalent of the conservation of angular momentum and therefore governs the
evolution of the warp. For lengthscales that are long compared to the vertical
scaleheight of the disc, the known non-resonant and resonant regimes of warp
dynamics, including the diffusive and wavelike regimes of Keplerian discs,
occur in the local model in the same way as in a global view of warped discs.
