The "Top" position of the NAS523 symbol is the most critical. It typically indicates the or the specific material and type of the fastener.
While many online summaries exist, the official is essential for several reasons: nas523 pdf top
It helps mechanics select the correct bucking bars and rivet sets for the job. Where to Find NAS523 Documentation The "Top" position of the NAS523 symbol is the most critical
5056 Aluminum Alloy (Used primarily with magnesium structures). KE: 7050 Aluminum Alloy. Why You Need the Official PDF nas523 pdf top
The code clarifies if the rivet is a universal head (protruding) or countersunk (flush).
Mention if you need or material substitutions.