Package orientation Mar ing are generally not necessary for Class 2 gases. However, when the cylinders are packed within combination packagings or overpacks and are not visible, in order to ensure correct handling and loading, it will be necessary to show the package orientation. The package orientation Mar ing is therefore not confined to cryogenic liquids only. Depending on the orientation of the cylinders and the manner in which they are assembled, the shipper May Dec de better to affix the orientation Mar ings. Package orientation labels May also be necessary to protect the valves depending on its orientation.