The main purpose of screws is to make industrial products form a fixed whole. In use, it often happens that the teeth cannot be closely connected with each other, the screw head breaks if the screws are locked too hard, or the teeth cannot be locked tightly due to poor tooth patterns, which is a problem of accuracy. Screws are "mass products", not handmade works of art. In mass production, they are supplied to consumers for the purpose of achieving high precision, stable quality and popular price.

Screws play an important role in industry. As long as there is industry on the earth, the function of screws will always be important. Screw is a common invention in people's production and life for thousands of years. According to the application field, it is the largest invention of mankind.