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nuts 
Metal parts with holes whose surfaces are threaded for screwing onto the corresponding bolts.
wing nut
Nut comprised of two protruding ends for tightening or loosening by hand.
acorn nut
Nut capped with a hollow dome that covers and protects the threaded end of the bolt.
hexagon nut
Most common nut; it has six sides for tightening with a wrench.
