ISO 17939:2015 specifies the classification, structure and main dimensions, materials, quality of manufacture, testing of watertightness and designation for oil tank hatches for application on board ships in order to ensure interchangeability of the hatches. The remaining dimensions, welding, and other details are left to the manufacturer. These hatches generally conform to the requirements of the International Convention on Load Lines 1966 (ILLC66). These structures and specifications of oil-tight hatch covers in this ISO 17939:2015 meet IACS UR S26 requirements. The possibility for application in position 1 and position 2 has to be considered for each situation and, where necessary, the hatch covers shall be provided with additional stiffening. ISO 17939:2015 is applicable to the design, manufacturing, and test of accommodation ladders, as well as accommodation ladder used specifically in combination with pilot ladder (hereinafter referred as "pilot accommodation ladder"). Users of ISO 17939:2015 should note that while observing the requirements of ISO 17939:2015, they should, at the same time, ensure compliance with such statutory requirements, rules, and regulations as may be applicable to the individual ship concerned.