The mechanical switching of ferroelectric domains is achieved in PbZr0.2Ti0.8O3 thin films obtained by the sol-gel method for thicknesses up to 200 nm. The dielectric polarization can be switched when a force higher than a given threshold value in the order of some µNewtons is applied with the tip of an atomic force microscope. This threshold is determined as a function of the thickness of the films, and local hysteresis loops are recorded under mechanical stress. The possibility of switching the polarisation in such unusually thick films is related to the existence in their volume of physical nanoscale defects, which might play the role of pinning centers for the domains.