The four main types of manufacturing processes are shearing and forming, in which an item is either cut into multiple pieces, like fabric or paper, or bent into a specific shape; joining, in which two items are connected, most commonly by welding; casting and molding, in which a substance such as plastic or glass is melted and shot into a mold; and machining, in which a tool cuts, shapes, or removes material from an object, for example by drilling a hole or etching threads onto a metal peg to make a screw.