What does it typically indicate if the engine "locks"?

A locked engine typically indicates that the internal components of the engine have seized, which is often caused by a lack of lubrication. When there is insufficient oil in the engine, it can lead to increased friction between moving parts. This friction generates excessive heat, which can cause components to expand and ultimately seize up, resulting in the engine locking. Proper oil levels are crucial for the engine's operation, as oil provides necessary lubrication, cooling, and cleaning to ensure that all parts function smoothly. While overheating can also lead to serious engine problems, insufficient oil is the most direct cause of an engine locking situation.