Elevation mechanisms for table saws and anti-backdrive mechanisms for use in elevation mechanisms for table saws are disclosed. The anti-backdrive mechanisms typically include three sub-assemblies: an input assembly, an output assembly, and a fixed assembly. The anti-backdrive mechanisms prevent a torque related to the output assembly from changing the blade elevation. For example, the weight of the blade and the structure supporting the blade is prevented from backdriving the elevation mechanism and allowing the blade to drop.