Specifies requirements for general purpose sheave blocks for lifting purposes that meet the performance requirements of the M3 group classification of crane mechanisms as specified in AS 1418.1. This Standard does not cover power-operated sheave blocks specifically for use with natural fibre ropes or synthetic filament ropes, sheave blocks used for lightweight lifting in the building industry and for general materials handling (known as 'gin blocks'). Guidance on information that should be supplied with enquiries and orders on care and use, on use of ships' cargo blocks and on use for non-lifting applications, is given in appendices.