The NAS523 rivet code, also known as the , is a standardized symbol system used in aviation blueprints to communicate precise fastener requirements within a single "plus" or "crosshair" symbol. The NAS523 Plus Symbol Layout

Example: Y=8 → 8/16" = 1/2" length.

This system eliminates language barriers and minimizes transcription errors on the shop floor, ensuring that the structural integrity of the aircraft is maintained exactly as designed by the Type Certificate Data Sheet (TCDS) or Structural Repair Manual (SRM). Anatomy of an NAS523 Rivet Code

Expressed in 1/16-inch increments. In 4-6 , the 6 means 6166 over 16 end-fraction 38three-eighths Key Rivet Materials and Standard Part Numbers

The standard, managed by the Aerospace Industries Association (AIA), defines a unified marking system used on engineering drawings to specify rivets. Instead of writing out lengthy descriptions for a rivet's material, diameter, countersink style, and length, engineers use a compact, cross-shaped quadrant symbol or a specific alphanumeric code.