A locking rod is used on a freezer rack to protect the boxes that are stored in the rack from falling out.  When removing racks from liquid nitrogen freezers or -80º C mechanical freezers, there is a tendency to tilt the top of the rack forward.  Without a locking rod, some or all of the boxes could slide out of the rack, causing scattered and damaged vials.

Other methods have been used for preventing boxes from sliding out of freezer racks.  One method is a small vertical metal lip (1/4-inch) on the front of the rack shelf.  Boxes can easily slide into the shelf, drop down over the lip and be prevented from sliding out.  The disadvantage of this method is in having to lift the box high enough to clear the lip.  The spacing of the rack around the box does not allow a person’s fingers to easily grab the box. 

Another method is a thin wire attached to the front metal “runners” and fastened to the shelves.  The wire is raised to allow access to the boxes or lowered to prevent the boxes from falling out.  The thin wires are bent and fastened in place to small holes in the “runners”.  The disadvantage of this method is that the small wires tend to catch on other racks in the freezer.