  We prove a three sphere inequality with optimal exponent at the boundary for
solutions to the Kirchhoff-Love plate's equation satisfying homogeneous
Dirichlet conditions. This result implies the Strong Unique Continuation
Property at the Boundary (SUCPB). Our approach is based on the method of
Carleman estimates, and involves the construction of an ad hoc conformal
mapping preserving the structure of the operator and the employment of a
suitable reflection of the solution with respect to the flatten boundary which
ensures the needed regularity of the extended solution. To the authors'
knowledge, this is the first (nontrivial) SUCPB result for fourth-order
equations with bi-Laplacian principal part.
