An analysis is made of the mechanical defects in KH2PO4 compatible with the crystal symmetry. With the theory of crystal dislocations, one can explain several experimental results on domain equilibrium states, domain velocities, and the critical electric field to move the domains in the plane perpendicular to the ferroelectric axis c. The most important result is the possible explanation in terms of mechanical phenomena of the long‐range interaction between domains, and domain freezing at low temperatures.