Ag(111) surface state electrons have been confined in symmetric and asymmetric Fabry-Perot resonators formed by two atomically parallel step edges. The local density of states in the resonators has been measured by means of low-temperature scanning tunneling spectroscopy and can perfectly be explained with a simple Fabry-Perot-like model. The energy dependent reflection amplitudes and scattering phase shifts of the different kinds of Ag(111) step edges have been determined with high accuracy. The model character of the resonators opens up quantitative electron scattering experiments at test structures brought into the resonator
