  The paper presents a novel view on the scattering of a flexural wave in a
Kirchhoff plate by a semi-infinite discrete system. Blocking and channelling of
flexural waves are of special interest. A quasi-periodic two-source Green's
function is used in the analysis of the waveguide modes. An additional
"effective waveguide" approximation has been constructed. Comparisons are
presented for these two methods in addition to an analytical solution for a
finite truncated system.
