What type of fastener is specifically designed to not come loose during operation?

A lock device is specifically designed to prevent loosening during operation, often in applications where vibrations or movements are present. This could include various forms such as lock nuts, which have added features like nylon inserts or serrated surfaces to grip tightly against the threads of a screw or bolt.

Lock devices are integral in ensuring the integrity of a joint by maintaining clamping force, which is particularly important in dynamic environments. Their design features, such as friction surfaces or additional locking mechanisms, are critical for applications where standard fasteners may become loose over time due to operational conditions.

In contrast, options like standard screws or regular nuts may not have these specific locking features, making them more susceptible to loosening under dynamic conditions. While rivets create a permanent mechanical connection, they do not provide the option for disassembly or adjustment, and thus do not fulfill the requirement of maintaining tightness in operations where loads may change.