The turn pin, code 100100, is a precision-engineered component used in the MAN L21/31 engine to facilitate controlled positioning, alignment, or rotational guidance of specific mechanical parts during assembly and maintenance operations. Designed to ensure accurate engagement and repeatable positioning, it plays an important role in maintaining correct geometry and preventing misalignment of critical components. Manufactured from high-strength, wear-resistant materials, the turn pin is capable of withstanding repeated use, mechanical loads, and operational stresses. Its reliability and precision contribute to efficient maintenance procedures, reduced risk of assembly errors, and the overall durability and performance of the engine.