One of the most common types is an overhead conveyor with the trolleys connected together with a chain. The chain can either be enclosed (“enclosed track”) or open below an I-beam. These style of material handling systems are installed in nearly every high volume production facility. The chain is driven by a motor with a gearbox, and the parts to be moved are suspended from trolleys attached to the chain. Many different attachment types are available. For complex parts, use a fixture or carrier suspended from several trolleys to locate the part in position. The chain can be always running, or alternatively the system can index. This moves parts from one assembly station to the next at a predetermined interval.