The screw identified by code number K 33421 serves as a locking component for the serrated bolt-locking device K 33420 in the Sulzer ZV40/48 engine. Though small, this screw is essential in maintaining secure connections under vibration-heavy conditions. By preventing loosening of the bolt-locking mechanism during engine operation, it plays a crucial safety role and ensures mechanical stability, especially in parts of the engine where high-speed rotation and repeated stress cycles are the norm.