A nut is a type of fastener with a threaded hole, typically used together with a bolt or screw to secure and fasten multiple parts.

Types of Nuts
Hex Nut – Most widely used standard nut
Lock Nut (Nyloc Nut) – Prevents loosening due to vibration
Flange Nut – Has a built-in washer for load distribution
Cap Nut (Acorn Nut) – Closed end for safety and appearance
Wing Nut – Hand-tightened, no tools required
Square Nut – Used in special applications

ISO 4032 – Hex nuts
DIN 934 – Hex nuts
ASME B18.2.2 – Hex nuts

Materials & Grades

Carbon Steel
Stainless Steel (SS304 / SS316) 
Brass
Alloy Steel

Sizes
Metric Sizes
M3, M4, M5, M6, M8, M10, M12, M16, M20, etc.

Inch Sizes
1/4", 3/8", 1/2", 3/4", etc.