On a bill of materials, what indicates which parts form each subassembly?

The part level number is essential for understanding how parts are organized within a bill of materials (BOM) because it designates the hierarchical relationship of components. In a BOM, the part level number signifies the specific level of each part in the assembly structure, indicating whether a part is a primary component, a subassembly, or a constituent part of a subassembly.

This organization helps in identifying which parts belong to which subassemblies. For instance, in a complex product that involves multiple layers of assembly, the part level numbers allow workers or systems to quickly determine how to group and piece together specific components. This clarity is crucial for efficient production and assembly processes, ensuring that all parts required for a subassembly are identified and can be effectively managed in manufacturing and inventory.

The other options pertain to different functions within the BOM or do not provide the hierarchical clarity necessary for subassembly identification. For example, part codes are unique identifiers for each component but don’t indicate their assembly relationships. The subassembly index may categorize assemblies but lacks the detailed hierarchy. Assembly instructions guide the assembly process but do not directly reference how parts relate in terms of structure within the BOM.