You can also find bolts with a locking nylon patch applied, like these from Nylok:
These are useful if the bolt is going into a blind threaded hole.
Added The Following
As I said in a comment below, these are considered superior to even locking adhesives in that chance of an assembler applying the wrong amount of locking compound is eliminated.
For our hi-rel applications, there's a specified process that's followed when using these, and similar fasteners, which include the following:
- The bolt is torqued to the proper setting, using a calibrated torque wrench. There are always two operators involved, one to do the tightening and another to witness that the proper torque was used.
- Depending on the application, we may apply a dab of structural adhesive to the head of the bolt to further ensure that it won't back out.