[Code of Federal Regulations] [Title 14, Volume 1] [Revised as of January 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 14CFR31.37] [Page 729] TITLE 14--AERONAUTICS AND SPACE CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 31--AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS--Table of Contents Subpart D--Design Construction Sec. 31.37 Fastenings. Only approved bolts, pins, screws, and rivets may be used in the structure. Approved locking devices or methods must be used for all these bolts, pins, and screws, unless the installation is shown to be free from vibration. Self-locking nuts may not be used on bolts that are subject to rotation in service.