The (National Aerospace Standard) is a set of guidelines, often used in drawing callouts, that defines a code for solid rivets and fasteners. It is primarily designed for aircraft sheet metal work and repairs where fasteners create permanent, non-removable deformations, ensuring the fastener must be destroyed for removal.

This article serves as a complete guide to the , explaining exactly what the standard is, why it is indispensable in aviation, how to interpret its coding system for rivets, and where you can find the official documentation.

Often identifies an MS20426AD rivet (countersunk 2117 alloy). ↗️ Northeast (NE): Diameter & Head Placement