The document summarizes information about rivets and gears. It defines a rivet as a metal pin for fastening two pieces of metal together. Rivets are made of materials like steel and are produced via forging. Rivets are used in applications requiring high joint strength, like ships and aircraft. Gears are defined as machinery that transfers motion between components. Gears are usually made of metals and manufactured via processes like molding, cutting, or 3D printing. Gears are used to change motion direction or speed in mechanical devices.