A nut is a type of fastener which has a threaded hole of various shapes. A nut is used in a bolt mechanism as a tool to tighten the entire assembly and to hold it in place. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts. In applications where vibration or rotation may work a nut loose, various locking mechanisms may be employed. The most common shape is hexagonal, for similar reasons as the bolt head - 6 sides give a good granularity of angles for a tool to approach from (good in tight spots), but more (and smaller) corners would be vulnerable to being rounded off.

DIN 934 Nuts	Brass Panel Nuts
Brass Lock Nuts	Brass Coupling Nuts
Heavy Hex Jam Nuts	Brass Heavy Hex Nuts
DIN 439 Brass Lock Nuts	Brass Check Nuts
Brass Spacer Nuts	Brass Cap Nuts DIN 1587
Brass Wing nuts	Brass Flanged Back Nuts Flange Nuts
Brass Square Nuts	Brass Metric Nuts
Acorn Nuts Brass	Insert Nuts Brass
DIN 557 Square Nuts