This Standard covers general and dimensional data pertinent to the various types of screw and captive washer assemblies, otherwise known as sems. The word sems is recognized in the United States as a generic term applicable to screw and washer assemblies. Also included in this Standard are appendices to illustrate the relative proportions of plain and conical washer sems and provide documentation on the washer dimensions for sems with screw types and head styles that have been relegated to not recommended for new design status.