When a mod is "locked," it's often protected by a password or specialized encryption that standard tools like 7-Zip or WinRAR can't penetrate. These mods appear as .scs or .zip files but will return errors if you try to extract them.
While SCS Software provides an official Game Archive Extractor for base game files, it specifically open locked community mods. To bypass these locks, the community relies on third-party software: SCS Unlocker For Locked Mods - Euro Truck Simulator 2 15l
Unlocking Potential: A Guide to SCS Unlockers for Euro Truck Simulator 2 (1.51) When a mod is "locked," it's often protected