Besides using optical readers at checkout stands , store personnel can use handheld wands attached to portable recording devices to replenish the store's inventory . When an item must be restocked , the wand reads the item's bar code that's fastened to the shelf ' where the item is displayed . This reading accurately enters the item description into the recorder . The clerk keys the quantity needed into the recorder . The recorder can then be connected by telecommunications lines to a warehouse computer system to complete the reordering procedure .