The first large sized container carrier in the world to use a new grade of higher tensile steel in its hull structure with a specified yield point of 47 kgf/mm (460N/mm) was built to NK class and delivered in June 2007. Known as YP47 steel, this comparatively strong and tough material is currently attracting much attention as an effective solution to the challenges presented by the use of extremely thick steel plates in the construction of the hull structures of container carriers that have been growing ever larger in size in recent years. ClassNK prepared these guidelines drawing upon the results of many years of research conducted into the practical application of YP47 steel and the experience gained from actual use of the material in the construction of large size container carriers.