WD-40 is used by many different people and industries for lubrication, rust prevention, moisture displacement, and loosening stuck parts.
Common users include:
Mechanics and automotive technicians
Electricians (to help protect metal parts from moisture and corrosion; avoid spraying on energized electrical equipment)
Plumbers
Maintenance technicians
Factory and workshop workers
Construction workers
Engineers
Farmers
Bicycle and motorcycle owners
DIY homeowners
Typical uses:
Loosening rusty nuts and bolts
Lubricating hinges, locks, and tools
Preventing rust on metal surfaces
Removing grease, dirt, and adhesive residue
Displacing moisture
WD-40 is a versatile maintenance product, but it is not a long-term lubricant for high-friction machinery or bearings. For those applications, a dedicated grease or machine oil is usually a better choice.