A screw or bolt with a threaded shaft and cylindrical head with a hexagonal head or recess for turning it with a wrench or driver. Widely used in machine tools and for assembling parts in automotive and aeronautical equipment.
Hex. Bolt (HB), Fillister Head, Hexagonal Head, Round Head, Flat (F or K), Round Washer (PW or N), Hex. Socket (HS), Slotted Recess (S), Hex. Socket Recess (HS), Fluted Socket Recess (FL), Crossed Recess (P)