11. Problems to avoid a. Ensure that no two items carry the same item number. b. Choose the correct size for the barcode symbol. c. Ensure that the size of the barcode is correct (see size guide). d. Reducing the height of the barcode (known as "truncation") will reduce its scanning capability and should be avoided. e. Respect the light margin areas. f. Keep the light margins clear of any dark colours or graphics. g. Choose a correct colour contrast. h. Some colour combinations scan more successfully than others (see colour wheel).