The generation of the density wave trains at the satellite resonance zones of the dense planetary rings is qualitatively understood (e.g., F. Shu, 1984, in Planetary Rings, pp. 513-561, Univ. of Arizona Press, Tucson, AZ), but the optically thin C-ring and the Cassini Division behave drastically differently: in some of the resonance locations isolated narrow ringlets are found, often embedded in a gap (G. L. Tyler et al., 1983, Icarus 54, 160-188). According to our numerical N-body simulations a single satellite can create a narrow ringlet with sharp outer and inner edges. In the experiments with a bimodal size distribution the large particles become more efficiently confined, in agreement with the observations where the fraction of small particles is found to be enhanced at the ringlet edges (Tyler et al. 1983).