What're Combination of parts and connecting parts?

Combination of parts and connecting parts: Combination of parts refers to a combination of a class of fasteners, such as a machine screws (or bolts, self-tapping screws) and flat washers (or spring washers, lock washers) combination of supply; connecting parts refers to a combination of some kind of special bolts, nuts and washers of a class of fasteners, such as high-strength bolts for steel structures with large hexagon bolts connecting parts.