As the grocery items moves along the conveyor belt, the checker passes each item over a glass plate in the counter top, making sure that the UPC symbols can be read by the laser beam under the glass.

• 食品杂货经传送带传到收款员跟前，收款员随即将每一物品搁在柜台上的一块玻璃板上一扫，好使板下的扫描机阅读条形码。