An assembly line is a manufacturing process (often called a progressive assembly) in which parts (usually interchangeable parts) are added as the semifinished assembly moves from workstation to workstation where the parts are added in sequence until the final assembly is produced. By mechanically moving the parts to the assembly work and moving the semi-finished assembly from work station to work station, a finished product can be assembled faster and with less labour than by having workers carry parts to a stationary piece for assembly.