The handling unit carton or case is not standardized, but generally it refers to a rectangular box that
• weighs between about 5 and 50 pounds (2.3–22.7 kilograms);
• can be handled by one person;
• is conveyable (which depends on the type of conveyor);
• can be stored on a pallet.
When handled in volume, cartons are typically stored on pallets and so
restocking is a unit-load process—but picking is not. This creates additional
complexities in our models of space and labor. One consequence is that it becomes
much more difficult to measure the convenience of an individual location;
but it is still possible to make broad distinctions.
The material flow on which we concentrate here is that of Figure 7.1