The analogy between the field-induced and flow-induced deformations of nematic liquid crystals is summarized. The threshold onset of the deformation occurring under rigid boundary conditions, the unwinding of the helical axis in a chiral nematic material, and the saturation threshold appearing for weak anchoring are described as examples of analogous phenomena which take place both in external fields and during shear flow. The analogy has allowed prediction of a new threshold effect possible in a sheared, weakly anchored nematic. The description of this effect is supported by numerical calculations. Stability analysis was also performed.