Main:
- Internal thread
- Permanent assembly of two sheets
- Blind installation
Secondary:
- Spacer
- Bearing
- Pin

Welded nut:
- a long, complex welding process
- internal thread presence not guaranteed
- coaxiality of internal thread not guaranteed
- an unattractive solution
Workpiece tapping:
- a long, complex and not very precise tapping process
- low mechanical thread resistance (not enough threads)
Nut and bolt:
- requires through hole drilling for tubes
- impossible to use on blind applications