The stopper plate K 34138 is a mechanical retaining and positioning component associated with the operating piston assembly of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Its principal function is to provide a defined mechanical stop or secure retention of associated components, helping maintain the intended position and movement limits of the operating piston mechanism. Although comparatively simple in form, a stopper plate can perform an important safety and reliability function because incorrect positioning or excessive movement within a mechanical assembly may lead to increased wear, misalignment, impact loading, or damage to neighboring parts. The K 34138 is therefore manufactured to accurate dimensions and from material capable of resisting repeated mechanical loading, vibration, and long-term operating stresses. Correct installation and inspection of the plate and its contact or fastening areas are important during maintenance. By preserving the designed mechanical limits and stability of the operating piston assembly, the K 34138 stopper plate contributes to predictable operation, reduced component wear, and dependable long-term engine service.