In this tutorial course of SHELXL, we will focus on how to treat the twinning by merohedry. Merohedral twinning is not apparent during the measurement or in the diffraction pattern, and therefore, unsolved twinning and fuzzy molecular structures remain in the data folder. We would like to show the avoidable pitfalls that are to be considered for the correct molecular structures using examples of solved merohedral twin crystals and step by step tutorials for organ(ometall)ic chemists.