"This SAE Aerospace Recommended Practice (ARP) is intended to interpret and clarify engineering drawing requirements relating to the manufacture and inspection of fluid system couplings@ tube fittings@ and hose ends. Because it is impractical to define every minute detail of the part on the face of the drawing@ this document describes interpretations of dimensioning of general machining features and otherwise undefined tolerances that fall under the heading of ""good shop practice"". This document serves as a supplement to engineering drawings when referenced on applicable documents."