A system includes a first mobile drive unit and a second mobile drive unit. The first mobile drive unit is operable to dock with a first item holder at a first end of a column of connected item holders. The second mobile drive unit is operable to dock with a second item holder at a second end of the column of connected item holders. The system also includes a management module that is operable to instruct the first mobile drive unit and the second mobile drive units to transport the column of connected item holders from a first location to a second location.