  An S matrix approach is developed to describe elastic scattering resonances
of systems where the scattered particle is asymptotically confined and the
scattering potential lacks continuous symmetry. Examples are conductance
resonances in microstructures or transmission resonances in waveguide
junctions. The generic resonance is shown to have the asymmetric Fano
lineshape. The asymmetry parameter q is independent of coupling to the
quasi-bound level implying a scaling property of the resonances which can be
tested in transport experiments.
