Directionally selective nonlinear transmission behavior has been observed for simple glass-based two-layer systems in $Z$-scan experiments employing femtosecond pulses at a wavelength of $\lambda =800\mathrm{nm}$. Glass sheets of 1 mm thickness with a very thin surface layer ($\sim 2\mathrm{\mu m}$) containing spherical Ag nanoparticles have been studied. In these samples, irradiating from the substrate side causes a strong transmission decrease via self-focusing of the beam and subsequent two-photon absorption in the thin layer, whereas the reverse direction may pass the sample without loss. This anisotropic optical limiting is discussed in terms of a numerical model in the limit of thin samples with respect to the Rayleigh range of the laser beam.