Although numerical simulations of flexible rockfall protection fences are common today, evaluating the reliability of such simulations remains a challenge. This contribution provides insight into and discusses certain finesses regarding the simulation of flexible rockfall protection fences. It identifies the bottlenecks of suitable simulation calibration and describes how to handle numerical effects which can cause non-realistic simulation results. The article not only gives an overview of the existing approaches used to simulate flexible barrier systems, but also introduces some detail on how the simulations work, which also serves as a form of evaluation manual for people confronted with simulation results.