Bolts and nuts are the most widely used fastener combinations. A bolt is a cylindrical rod with external threads, with a head at one end for applying 

torque; a nut is a hole piece with internal threads.

The core of their collaborative work lies in the threads. When the nut is screwed onto the bolt, its inclined thread surface converts rotational force 

into a powerful axial clamping force. Rotating the nut clockwise, it descends along the thread spiral of the bolt, compressing the connected parts 

under the bolt head, thereby firmly securing multiple components together. This design utilizes the "screw" principle of labor saving and can generate 

a huge pre-tightening force far exceeding the rotational force. Its self-locking feature ensures stable connection even in vibrating environments.