Boxcars can carry most kinds of freight. Originally they were hand-loaded, but in more recent years mechanical assistance such as forklifts have been used to load and empty them faster. Their generalized design is still slower to load and unload than specialized designs of car, and this partially explains the decline in boxcar numbers since World War II. The other cause for this decline is the dramatic shift of waterborne cargo transport to container shipping. Effectively a boxcar without the wheels and chassis, a container is designed to be amenable to intermodal freight transport, whether by container ships, trucks or flatcars, and can be delivered door-to-door.