Nuts are threaded fasteners that are used with bolts to fasten multiple parts together. Nuts and bolts work together, with their threaded friction and the stretch and compression of parts, to securely hold items in place. Washers are thin, disk-shaped plates that are often used with nuts and bolts to more widely distribute the load. Common materials used for nuts, bolts, and washers include carbon steel, alloy steel, stainless steel, and nickel alloys.

2.  A nut is a type of hardware fasteners with a threaded hole.
Nuts are almost always used opposite a mating bolt to fasten a
stack of parts together.
 The two partners are kept together by a combination of their
threads' friction, a slight stretch of the bolt, and compression
of the parts.
 A washer is a thin plate typically disk-shaped with a hole that
is normally used to distribute the load of a threaded fastener.

3.  Carbon steel and Alloy steel material used for Nut &
Bolt manufacturing.
 Nut mfg by Blanking and Threading. Bolt by forging
and threading.

4. Nickel Alloy Standard : ASTM / ASME SB 160 / 164 / 425 / 166 / 446 / 574 / 472
Grade : UNS 2200 / UNS 2201, UNS 4400 , UNS 8825 , UNS 6600
Stainless Steel : Standard : ASTM / ASME A/SA 193 / 194
Grade : B 8 (304), B 8C (SS 347), B 8M (SS 316), B 8 T (SS 321), A 2, A 4
Alloy Steel : Standard : ASTM / ASME A/SA 193 / 194 GR.
Grade : B 6, B 7/ B 7M, B 16, 2, 2HM, 2H, GR 6, B 7, B 7M.

6. Nut

8. Washer

9. TEE Bolt Stud Bolt Expansion Bolt
U-Bolt Hexagonal Bolt