Careless adjusting methods to increase or decrease retention by grinding, polishing, or bending the clasp arm can lead to instability of the removable partial denture, damage to the surrounding tissues, and fracture of the clasp arm. This article describes systematic evaluation criteria and adjusting methods of retention force of a cast clasp. Excessive retention can be reduced by using a proper adjustment method, which depends on the cause. Poor retention can be increased temporarily, but it will decrease again. Evaluations and adjustment of poor retention will contribute to the diagnosis of the cause and will establish clinical and laboratory procedures that will lead to making clasps with proper retention in the future.